For each of the following, find a differential equation with the given solution. (Hint: Use what you know about characteristic polynomials) (a) y(t) = c1e−t + c2e−4t (b) P(t) = c1e2t + c2te2t (c) y(t) = c1cos(5t) + c2sin(5t) (d) P(t) = c1et + c2e−2t + c3e6t