Problem 2

In the previous problem, our product $A^3 X_0$ is not a whole number, it may due to the multipation of $A^3$, therefore, we apply adifferent method,in solving the following problems.

Assume that in a group of 550 people, 200 are interested in mathematics and 350 are interested in biology. Every year 8 % of Mathematics fan change their heart to biology and only 4 % of Biology lovers change their heart to mathematics.
a) How many of these people are interested in mathematics 15 years later? b)How many of these people are interested in biology after 20 years ?