Questions 18 thru 20 reference the following linear programming formulation Diet Problem Four types of animal feed are mixed to create a custom blend. Nutrient information is listed below: Nutrient Feed Feed Feed Feed #1 #2 #3 #4 [X1] [X2] [X3] [X4] Corn 30% 5% 20% 10% Grain 10% 30% 15% 10% Minerals 20% 20% 20% 30% Cost / Pound $0.25 $0.30 $0.32 $0. 15 The customer wants 8,000 pounds of custom feed with at least 18% corn, at least 15% grain, and at least 22% minerals. How many pounds of each feed should be mixed together to achieve these goals at minimum cost? 18. What is the objective function? a. Maximize 0.25X1 + 0.30X2 + 0.32X3 + 0.15X4 b. Minimize 1.25X1 + 1.30X2 + 1.32X3 + 1.15X4 c. Minimize 0.25X1 + 0.30X2 + 0.32X3 + 0.15X4 d. Not enough information is provided e. None of the above 19. What is the constraint on corn if exactly 8,000 pounds of feed are produced (specific form)? a. X1+ X2 + X3 + X4 2 8000 b. 0.30X1 + 0.05X2 + 0.20X3 + 0.10X4 2 1440 c. 0.30X1 + 0.05X2 + 0.20X3 + 0. 10X4 2 8000 d. Not enough information is provided e. None of the above 20. What is the constraint on corn if the total amount of feed is not known (general form)? a. 1.12X1 - 1.13X2 + 1.02X3 - 1.08X4