Find the general solutions of the systems whose augmented matrices are given in Exercises 7-14. [1 0 -1 -7 0 7 0 1 -4 6 -2 2 5 -3 7] In Exercises 19 and 20, choose h and k such that the system has (a) no solution, (b) a unique solution, and (c) many solutions. Give separate answers for each part. 20. x_1 + 3x_2 = 2 3x_1 + hx_2 = k