Well, if it is increasing at a fixed rate of 2 mm/s, then the volume would still be increasing at a rate of 2 mm/s when the diameter is 80 mm, if I understand your question correctly.
Answer:
the answer is 2827.4
Step-by-step explanation:

Let x = speed of the first car
the second car is 12 km slower so the seconds car speed is x-12
they each drove 2 hours so 1st car = 2x
2nd car = 2(x-12)
they drove 360 km
so you have 2x + 2(x-12) = 360
solve for x
2x+2(x-12) = 360
2x + 2x-24 = 360
4x-24 = 360
4x = 384
x = 384/4
x = 96
1st car drove at 96 km per hour
slower car drove at 96-12 = 84 km per hour
Answer:
V≈1282.82
Step-by-step explanation:
V=πr^2h
3=π·72·25
3≈1282.817