A radioactive isotope decays to a more stable isotope a rate proportional to the square of the remaining radioactive isotope. Let m(t) represent the amount of radioactive isotope after t years. If the initial mass of the radioactive isotope was 20g:

a) Set up an initial value problem to describe the situation.

b) If the proportionality constant has been found to be 1, solve the IVP determined in part a).