Let A , , , , and . (a) Find and use it solve the four equations Ax, Ax ,Ax, and Ax. (b) The four equations in part (a) can be solved by the same set of operations, since the coefficient matrix is the same in each case. Solve the four equations in part (a) by row reducing the augmented matrix [A ]. Find . Select the correct choice below and, if necessary, fill in the answer boxes to complete your choice A. (Simplify your answers.) B. The matrix is not invertible. Solve Ax. x (Simplify your answers.) Solve Ax. x (Simplify your answers.) Solve Ax. x (Simplify your answers.) Solve Ax. x (Simplify your answers.) (b) Solve the four equations by row reducing the augmented matrix [A ]. Write the augmented matrix [A ] in reduced echelon form. (Simplify your answers.)