4. (15 pts) Suppose that the assembled stiffness equations for a one-dimensional finite element model before [210] imposing constraints are -12 -1 0 -1 11-0 U This system is to be solved subject to the multipoint constraint u, = U,. (1) Impose the constraint by the master-slave method taking u, as master, and solve the resulting 2x2 system of equations. (2) Impose the constraint by the penalty function method, leaving the weight w as a free parameter. Write down the equation only and do not solve. (3) Impose the constraint by the Lagrange multiplier method. Show the 4x4 multiplier-augmented system of equations.