During a 1.5-hr storm, 1.3 in. of rain fell during the first hour, and 0.4 in. of rain fell during the last half hour. The average flow in the downspouts was 1.7, 3.6, and 3.4 ft3/sec for each of the half-hour periods. If the rooftop was 3 acres, how deep was the water on the roof at the end of each half-hour period?