An oil tank is being drained for cleaning. After t minutes there are V litres of oil left in the tank, where V(t) = 40(20-t)^2, 0 ≤ t ≤ 20. Determine the rate of change of volume at the time t=10 mins.

a) -800 L/min

b) -600 L/min

c) -400 L/min

d) -200 L/min

I choose a. I found the derivative and plugged in 10. I was just a bit confused with the restriction.

Julius Feb 23, 2018