Letter to a Friend: (5 points). As usual, explain your solutions to the following problems in the form of a letter to a friend. The ends of a chain of uniform density are attached to the tops of two vertical poles with equal heights that are placed 2b feet apart. The chain hangs in equilibrium in a uniform gravitational field, with the only other external forces being the two exerted by the poles on the end of the chain. With a, b > 0, and c E R constants having units of feet, the function h = f(x) = a cosh(x/a) +c, -b