78. From 1020, 3 March, to 1845, 5 March, your vessel steamed an observed distance of 845.6 miles. The average RPM was 78, and the pitch of the propeller was 20'03″. What was the slip?

The slip is calculated as the difference between theoretical and actual speed, resulting in approximately 3.8%, which rounds to 4%. This positive value indicates the propeller is not advancing as far as theoretically predicted, aligning with answer choice D.