Efficiency physics problem

Question

84 An internal combustion engine consumes 1 gallon of diesel fuel per hour. It provides a constant 10 hp. One gallon of diesel fuel has potential energy of about 115,000 Btu. Remember that 1 hp × 42.44 = 1 Btu/min. What is the efficiency of the system?

A. 22% Answer B. 28% C. 31% D. 35%

How I approach this Since 1 gallon an hour is 115,000 then 10hp constant an hour is 424.4 There I use output/input x100. So $424.4/100000 * 100$ I got .42 I am confused in where I went wrong?

Answer 1

First: read carefully the following statement from the problem:

Remember that $1$ hp × $42.44$ = 1 Btu/${\bf min.}\;$ [Bold-face mine.]

There are $60$ minutes in an hour.

Second: where are you making use of the information regarding potential energy of $\;115,000\;$ BTU?