Solve the following linear systems by Gauss elimination, with partial pivoting if necessary (but without scaling). Show the intermediate steps. Check the result by substitution. If no solution or more than one solution exists, give a reason.

3.2x₁ + 1.6x₂                            = -0.8
1.6x₁ - 0.8x₂ + 2.4x₃               = 16.0
             2.4x₂ - 4.8x₃ + 3.6x₄  = -39.0
                          3.6x₃ + 2.4x₄  = 10.2