The tax on a commodity is diminished by 22% but its consumption is increased by 9%. Find the decrease percent in the revenue derived from it?  Choose the correct answer:
A) 20 %  B) 18 %  C) 15 %  D) 12 %  E) 14 %

Rationale: "100 * 100 = 10000 78 * 109 = 8502 10000 - - - - - - - 1200 100 - - - - - - - ? = 15 % answer : c"
Answer: C