24 Recall the Dakota LP discussed in Chapter 6. Let v(L, FH, CH) be the maximum revenue that can be earned when L sq board ft of lumber, FH finishing hours, and CH carpentry hours are available.

a Show that v(L, FH, CH) is a concave function.

b Explain why this result shows that the value of each additional available unit of a resource must be a nonincreasing function of the amount of the resource that is available.