For part a), take the differential equation and separate variables, all the y terms and dy on the left, and k dt on the right, then integrate. For the left hand side you will have to use partial fractions but since it is already factored, it should not take a lot of effort.

After successfully integrating, try to write the relationship in the form as given in the problem.

For part b) use the two conditions and the 'asymptote' to determine the coefficients. I hope this helps!