The ratio of a to b is 4 to 5, where a and b are positive. If x equals a increased by 25 percent of a, and m equals b decreased by 80 percent of b, what is the value of m/x? Choose the correct choice from the following choices
A) 1 / 5 B) 3 / 4 C) 4 / 5 D) 5 / 4 E) 3 / 2

Rationale: "a / b = 4 / 5 m / x = ( 1 / 5 ) * 5 / ( 5 / 4 ) * 4 = 1 / 5 the answer is a ."
Answer: A