15 13. y" + -y' y =0 has solutions of the form y = r. Give a fundamental set of solutions and find their Wronskian. (a) {x 5, x ]; W = 8-3 (b) {x 3, x ]; W = 8 (c) {x-5, x 3 ]; W = 21-9 (d) {e-ba, e3x]; W = 2e-21 (e) None of the above