Two Engines Are Identical Except That Engine a Is Two

Multiple Choice

Two engines are identical except that engine A is two years old and engine B is new. If engine A does 15% less work than engine B under identical operating conditions, what is the ratio of the efficiencies of the two engines, e_A/e_B?

A) 0.10
B) 0.15
C) 0.85
D) 0.90
E) 1.0