Please give me correct solution.

Attenuateon You acquire a spectrum using the MCA for 200 s for the Cs137 source with no absorber. Setting a region of interest on the photopeak the Net Area is found to be 82075. Then a thin lead absorber is placed between the source and the detector and another spectrum acquired. This time the Net Area is 79606. Another thicker absorber is used and the Net Area found to be 39077. If the lead sheets are 0.032 and 0.25 inches thick respectively then determine the attenuateon coefficient of lead at 662 keV. Just use the two measurements with lead and give your answer to 2 decimal places in units of cm-1