Consider a mathematical program with constraints x1 - 2x2 + 3x3 … 25 x1, x2, x3 Ú 0 Determine the maximum step (possibly + ) that preserves feasibility in the direction indicated from the point specified. Also indicate whether that step indicates that the model is unbounded, assuming that directions improve everywhere.

(a) x = 1 -1, 3, -22 from x = 14, 0, 62

(b) x = 1 -2, 1, -12 at x = 18, 5, 32

(c) x = 11, 3, 12 from x = 10, 0, 42

(d) x = 12, 7, 42 at x = 120, 4, 32