Return to the problem of Exercise 1-3 and assume that t1 = 10, t2 = 20, c1 = 500, c2 = 100, b = 3, and T = 40. Determine (if necessary by trying all the possibilties) whether each of the following is a feasible and/or optimal solution.

(a) x1 = 0, x2 = 3

(b) x1 = 2, x2 = 1

(c) x1 = 3, x2 = 0