*12. Suppose that {(0, a)} = a for a > 0 and that f is defined by 0, x 0; 1, 0 < x < 2; Compute ff du. *13. Define the f(x) = , 0, 2 x < 5; x > 5. *12. Suppose that {(0, a)} = a for a > 0 and that f is defined by 0, x 0; 1, 0 5. Compute ff du. *13. Define the f(x) = , 0,