How to calculate and plot the transmitted light intensity through the pinhole as a function of Z of a confocal microscope system?

For a simple confocal microscope system shown below plot the transmitted light intensity
through the pinhole as a function of Z for these cases; pin hole size =1/2 A.U., 1 A.U.,
and 2 A.U.
Assume wavelength of 500 nm, N.A of 1
0