I am not sure which one is which

Acircle has a circumference of 28.36 units what is the diameter of the circle

Which expression is equivalent to 3^3 + 2^2?

Use the method of cylindrical shells to find the volume v generated by rotating the region bounded by the curves about the given axis. y = 7ex, y = 7e^-x, x = 1; about the y-axis