4. Consider the following system of equations with real coefficients: -3x1 x1 - +6x2 2x2 2x3 +6x4 +x3 = -10 = 7 - X3 -2x4 = 1 (a) Write down the associated augmented matrix. (b) Find the Reduced Row Echelon Form (RREF) of the augmented matrix found in (a). Write down the elementary row operations used to do the row reduction. (c) Find the general solution to the system of equations.