1. A shipping crate has a square base with sides of length x feet, and it is half as tall as it is wide. If the material for the bottom and sides of the box costs $2.00 per square foot and the material for the top costs $1.50 per square foot, express the total cost of material for the box as a function of x?

2. An agency charges $100 per person for a trip to a concert if 30 people travel in a group. But for each person above the 30, the amount charged each traveler will be reduced by $2.00. If x represents the number of people above the 30, write the agency's revenue R as a function of x?

3. A company handles an apartment building with 50 units. Experience has shown that if the rent for each of the units is $720 per month, all of the units will be filled, but one unit will become vacant for each $20 increase in the monthly rate. If x represents the number of $20 increases, write the revenue R from the building as a function of x?