A fraction in reduced form is such that when it is squared and then its numerater is increased by 25% and the denominator is reduced to 80% it results in 5/8 of the original fraction. The product of the numerator and denominator is:

a) 6
b) 10
c) 7
d) 12

Mixture Problem:
A mixture of M litre which contain two liquids A and B in the ratio a:b. Now the x litres of A from the mixture is taken out and replaced with an equal amount of mixture B. This process is repeated twice. Find the ratio of the amount of Liquid A left finally to that in the original mixture?

a)(x-M)/M^2
b)(M-x)/M^2
c) ((M-x)/M)^2
d)((1-x)/M)^2