The upper limit of integration for x, is not clear . So I will solve for two possibilities. Please take what ever is relevant to you. This is a double integral.
If the upper limit for x is "a", then the solution is simpler.
If the upperlimit in the integration is a, ie., y = a then:
I1 = πa²/4
Now the integral is :
If the upper limit for integration wrt x is not "a", but is "y", then the solution is more complicated. So we have :