Estimate the radar cross-section of rain for a side-looking airborne SAR operating in the L band at 1.5 GHz. The rain is specified by a range resolution of 15 m, an azimuth resolution of 18 m, and a rain elevation cell resolution of 20 m. The rain rates are 0.25 mm/hr, 1 mm/hr, 4 mm/hr, and 16 mm/hr.