13. (Crossing ) In general, we say that two projects with cash flows x, and y,,i = 0, 1, 2,... n, cross if xo yo and oo. Let P,

(d) and Py

(d) denote the present values of these two projects when the discount factor is d

(a) Show that there is a crossover value c>0 such that P,

(c) = P(c).

(b) For Exercise 11, calculate the crossover value c