Beth's class party was held in a steamboat on a local lake. The steamboat made a circuit of the lake at a constant rate of 16 mph. It traveled a total of 40 mi. around the lake. How long did the trip on the steamboat last?

(A) 2.5 hr.

(B) 3 hr
.
(C) 4.2 hr.

(D) 5 hr.​