Write the lowest-degree polynomial function that has the given set of zeros and whose graph has the given y-intercept.
a. zeros: x = - 4, x = 5, x = - 2 (double root); y-intercept: - 80
b. zeros: x = - 4, x = 5, x = - 2 (double root); y-intercept: 160
c. zeros: x = 1/3, x = -2/5, x = 0; y-intercept: 0
b. zeros: x = - 5i, x = - 1 (triple root), x = 4; y-intercept: -100