The tax on a commodity is diminished by 20% and its consumption increased by 15%. The effect on revenue is?
Pick: A) 9 % decrease B) 8 % decrease C) 6 % decrease D) 1 % decrease E) 2 % decrease

Rationale: "100 * 100 = 10000 80 * 115 = 9200 - - - - - - - - - - - 10000 - - - - - - - - - - - 800 100 - - - - - - - - - - - ? = > 8 % decrease answer : b"
Answer: B