Engine cylinder 15 cm deep, being bored out

radius increases by .10 mm/min

How fast does volume change when dia is 9.5 cm?

pi(r^2)h = V

pi(4.25)^2(15) = 851.12 cm^3

dr/dt = .01 cm

dv/dt = ?

f'gh + fg'h + fgh'

f' = pi

g' = 2r(dr/dt)

h' = dh/dt

pi(4.25^2)(15) + (pi)((4.25)(0.01) + (pi)(r^2)(1) = 911.91 cm^3

which is very wrong. Where did I go wrong? thanks.