Assume the internal energy of an elastic fiber under tension (see Problem 6.16) is given by. dU = T dS – P dV – F dl.  Obtain an expression for, (∂g/∂L)_P,T and calculate the maximum non-expansion work obtainable when a collagen fiber contracts from [1] = 20.0 to 10.0 cm at constant P and T. Assume other properties as described in Problem 6.16.