a)dV/dr=2pi*rh
b)dV/dr=2pi*(5)(40)
When the radius of the blood vessel is 40mm, the volume of the blood is increasing at 2pi*(5)(40) mm^2 per 5 mm change in radius
3)dV/dr=2pi*(6)(40)
When the radius of the blood vessel is 40mm, the volume of the blood is increasing at 2pi*(6)(40) mm^2 per 6 mm change in radius
d)dV/dr=2pi*(9)(40)
When the radius of the blood vessel is 40mm, the volume of the blood is increasing at 2pi*(9)(40) mm^2 per 9 mm change in radius
You'll have to calculate the values...