Solve the system of linear equations, using the Gauss-Jordan elimination method. (If there is no solution, enter NO SOLUTION. If there are infinitely many solutions, express your answer in terms of the parameters t and/or s.) 2x1 + 6x2 − 5x3 = 5 x1 + 3x2 + x3 + 7x4 = −1 3x1 + 9x2 − x3 + 13x4 = 1 (x1, x2, x3, x4)