9. What is the value of c?

A 80
B 50
C 100
D 84

With #! i’ve tried to figure it out but i can’t.

The number of revolutions of two pulleys is inversely proportional to their diameters. if a 24-inch diameter pulley making 400 revolutions per minute is belted to an 8-inch diameter pulley, find the number of revolutions per minute of the smaller pulley.

Solve the equation w^3 = 1,000 i honestly dont know how to punch this into a calculator pls