Exercise 1 (12 points.). Show that, for all m > 0, we have ged(ma, mb) = m ged(a,b). Exercise 2 (9 points). Find all the zero-divisors on Zs. For each zero-divisor, find a non-zero element of Zis that multiplies to zero with the zero-divisor. Exercise 3 (15 points). Solve the following linear congruences. (a) 131x11 (mod 1979). (b) 127x=11 (mod 1091). (c) 3x=12 (mod 21). (d) 6x=12 (mod 15). (e) 2x7 (mod 10).