Hi. I'm having trouble with this question:

Oil is spilling from a platform at a constant rate Q and forms a circular spot of constant thickness 10cm. It is observed that when the radius is 100m the radius is changing at a rate of 5 m/hr.

a) How fast is the area of the spill changing at this instance?

b) calculate the value of Q.

My attempt

a) where

so m^2/hr

b) I'm not sure what is Q...

does it have anything to do with

where

therefore, m^2/h

any help would be great!