A refinery blends three petroleum components into three grades of gasoline –regular, premium, and diesel. The maximum quantities available of each component and the cost per barrel are as follows: Component Cost/Barrel Maximum Barrels Available/Day A 9 6,000 B 7 3,000 C 10 4,500 To ensure that each gasoline grade retains certain essential characteristics, the refinery has put limits on the percentages of the components in each blend. The limits, as well as the selling prices for the various grades, are as follows:
Grade Selling Price/Barrel Component Specifications
R (regular) 18 Not less than 30% of A
Not more than 30% of B
Not less than 30% of C
P (premium) 25 Not less than 60% of C
A (diesel) 15 Not more than 50% of B
less than 10% of A
The refinery wants to produce at least 5,000 barrels of each grade of gasoline. The management wishes to determine the optimal mix of the three components that will maximize profit.
a. Define the decision variables.
b. Build an objective function.
c. Build all the constraints.

Areal estate agent is considering changing her cell phone plan. there are three plans to choose from, all of which involve a monthly service charge of $20. plan a has a cost of $.42 a minute for daytime calls and $.17 a minute for evening calls. plan b has a charge of $.52 a minute for daytime calls and $.15 a minute for evening calls. plan c has a flat rate of $80 with 275 minutes of calls allowed per month and a charge of $.38 per minute beyond that, day or evening.a. determine the total charge under each plan for this case: 150 minutes of day calls and 70 minutes of evening calls in a month. (do not round intermediate calculations. round your answer to 2 decimal places. omit the "$" sign in your response.)c. if the agent will use the service for daytime calls, over what range of call minutes will each plan be optimal? (round each answer to the nearest whole number.include the indifference point itself in each answer.)d. suppose that the agent expects both daytime and evening calls. at what point (i.e., percentage of total call minutes used for daytime calls) would she be indifferent between plans a and b?

Decision alternatives should be identified before decision criteria are established. are limited to quantitative solutions are evaluated as a part of the problem definition stage. are best generated by brain-storming.

Which statement best describes entrepreneurship aitmakes people very rich b it relies on large financial investments c it is only possible in the retail industry d it requires creativity and ambition