and here is marvin’s conversation with the tank, its gonna be a bit long so be patient :

Marvin stood at the end of the bridge corridor. He was not in
fact a particularly small robot. His silver body gleamed in the
dusty sunbeams and shook with the continual barrage which the
building was still undergoing.

He did, however, look pitifully small as the gigantic black tank
rolled to a halt in front of him. The tank examined him with a
probe. The probe withdrew.
Marvin stood there.

“Out of my way little robot,” growled the tank.

“I’m afraid,” said Marvin, “that I’ve been left here to stop
you.”

The probe extended again for a quick recheck. It withdrew again.

“You? Stop me?” roared the tank. “Go on!”

“No, really I have,” said Marvin simply.

“What are you armed with?” roared the tank in disbelief.

“Guess,” said Marvin.

The tank’s engines rumbled, its gears ground. Molecule-sized
electronic relays deep in its micro-brain flipped backwards and
forwards in consternation.

“Guess?” said the tank.

“Yes, go on,” said Marvin to the huge battle machine, “you’ll
never guess.”

“Errmmm …” said the machine, vibrating with unaccustomed
thought, “laser beams?”

Marvin shook his head solemnly.

“No,” muttered the machine in its deep guttural rumble, “Too
obvious. Anti-matter ray?” it hazarded.

“Far too obvious,” admonished Marvin.

“Yes,” grumbled the machine, somewhat abashed, “Er … how about
an electron ram?”

This was new to Marvin.

“What’s that?” he said.

“One of these,” said the machine with enthusiasm.

From its turret emerged a sharp prong which spat a single lethal
blaze of light. Behind Marvin a wall roared and collapsed as a
heap of dust. The dust billowed briefly, then settled.

“No,” said Marvin, “not one of those.”

“Good though, isn’t it?”

“Very good,” agreed Marvin.

“I know,” said the Frogstar battle machine, after another
moment’s consideration, “you must have one of those new Xanthic
Re-Structron Destabilized Zenon Emitters!”

“Nice, aren’t they?” said Marvin.

“That’s what you’ve got?” said the machine in considerable awe.

“No,” said Marvin.

“Oh,” said the machine, disappointed, “then it must be …”
“You’re thinking along the wrong lines,” said Marvin, “You’re
failing to take into account something fairly basic in the
relationship between men and robots.”

“Er, I know,” said the battle machine, “is it …” it tailed off
into thought again.

“Just think,” urged Marvin, “they left me, an ordinary, menial
robot, to stop you, a gigantic heavy-duty battle machine, whilst
they ran off to save themselves. What do you think they would
leave me with?”

“Oooh, er,” muttered the machine in alarm, “something pretty damn
devastating I should expect.”

Expect!” said Marvin, “oh yes, expect. I’ll tell you what they
gave me to protect myself with shall I?”

“Yes, alright,” said the battle machine, bracing itself.

“Nothing,” said Marvin.

There was a dangerous pause.

“Nothing?” roared the battle machine.

“Nothing at all,” intoned Marvin dismally, “not an electronic
sausage.”
The machine heaved about with fury.

“Well, doesn’t that just take the biscuit!” it roared, “Nothing,
eh? Just don’t think, do they?”

“And me,” said Marvin in a soft low voice, “with this terrible
pain in all the diodes down my left side.”

“Makes you spit, doesn’t it?”

“Yes,” agreed Marvin with feeling.

“Hell that makes me angry,” bellowed the machine, “think I’ll
smash that wall down!”

The electron ram stabbed out another searing blaze of light and
took out the wall next to the machine.

“How do you think I feel?” said Marvin bitterly.

“Just ran off and left you, did they?” the machine thundered.
“Yes,” said Marvin.

“I think I’ll shoot down their bloody ceiling as well!” raged the
tank.

It took out the ceiling of the bridge.

“That’s very impressive,” murmured Marvin.

“You ain’t seeing nothing yet,” promised the machine, “I can take
out this floor too, no trouble!”

It took out the floor, too.

“Hell’s bells!” the machine roared as it plummeted fifteen
storeys and smashed itself to bits on the ground below.

“What a depressingly stupid machine,” said Marvin and trudged
away.