If f (x) has integer coefficients and m is an integer solution of the polynomial equa- tion f(x) = 0, then for any n we can reduce both m and the coefficients of f (x) modulo n, and the equation becomes a congruence that still holds. For the follow- ing equations, verify that the given roots modulo 3 and 5 are in fact all such roots. Use this information to eliminate some of the integer roots, and then find all integer roots. (a) x3 - 7x2 + 4x -28 = 0 (roots are 1 (mod 3) and 1, 2 (mod 5)). (b) x3 - 9x2 + 10x - 16 = 0 (roots are 2 (mod 3) and 3 (mod 5))