A man travels m feet due north at 2 minutes per mile. He returns due south to his starting point at 2 miles per minute. The average rate in miles per hour for the entire trip is:
<spanclass=′latex−bold′>(A)</span>75<spanclass=′latex−bold′>(B)</span>48<spanclass=′latex−bold′>(C)</span>45<spanclass=′latex−bold′>(D)</span>24<spanclass=′latex−bold′>(E)</span>impossible to determine without knowing the value of m