An Outboard Motor for a Boat Is Cooled by the Lake

An outboard motor for a boat is cooled by the lake water at 15 ^$\circ$ C with a compression ratio of 10.Assume that the air is a diatomic gas.Calculate the efficiency of the Otto cycle.

A) 30%
B) 40%
C) 50%
D) 60%
E) 70%