Solve the system of equations using matrices. Use the Gaussian elimination method with back-substitution. 3a - b + 2c= -1 2a - b + 3c= -3 a + 2b + 4c= 1 . . . . . Use the Gaussian elimination method to obtain the matrix in row-echelon form. Choose the correct answer below. O A. 10 -1 2 O B. 10-5 2 0 1 -5 7 0 1 7 0 0 1 - 1 0 0 1 1 O C. 1 0 2 -1 OD. 1 1 - 1 2 0 1 -5 7 0 1 -5 7 0 0 1 0 0 1 The solution set is