The tax on a commodity is diminished by 20% but its consumption is increased by 20%. Find the decrease percent in the revenue derived from it?	Pick one
A) 20 %	B) 18 %	C) 4 %	D) 12 %	E) 14 %

Rationale: "100 * 100 = 10000 80 * 120 = 9600 10000 - - - - - - - 400 100 - - - - - - - ? = 4 % answer : c"
Answer: C