An Engine on a Test Stand Was Operated at Two

Multiple Choice

An engine on a test stand was operated at two fixed settings, each with an appropriate load. At the first setting, fuel consumption was 1 gal every 15 min. At the second setting, it was 1 gal every 20 min. The test took 10 h, and 37 gal of fuel were used. How long did the engine run at each setting?

A) The engine ran for 7 h at the first setting,
The engine ran for 3 h at the second setting.
B) The engine ran for 3 h at the first setting,
The engine ran for 7 h at the second setting.
C) The engine ran for 7.5 h at the first setting,
The engine ran for 2.5 h at the second setting.
D) The engine ran for 4 h at the first setting,
The engine ran for 6 h at the second setting.
E) The engine ran for 6 h at the first setting,
The engine ran for 4 h at the second setting.