12 Which of the following are NLP models, and why?

Are any of these quadratic programming models?

(a) Maximize profit = 3X1 + 5X2 + 99X3 subject to the contraints X1 Ú 10 X2 … 5 X3 Ú 18

(b) Maximize profit = 25X1 + 30X2 + 8X1X2 subject to the contraints X1 Ú 8 X1 + X2 Ú 12 X1 - X2 = 11

(c) Maximize profit = 3X1 + 4X2 subject to the contraints X21

- 5X2 Ú 8 3X1 + 4X2 Ú 12

(d) Maximize profit = 18X1 + 5X2 + X22 subject to the contraints 4X1 - 3X2 Ú 8 X1 + X2 Ú 18