The  purpose  of  a  production possibilities curve is  to  show  between  the  production of  two things.

trade-offs

relationship

similarities

price differential

Regina has enough money to buy all the items she needs 

3 cans of dog food = 1.50*3 = 4.50
1 gallon of milk = 4.00*1 = 400
5 pounds of chicken = 1.55*5 = 7.75
1 box of cereal = 2.75*1 = 2.75
6 rolls of paper towels = .99*6 = 5.94

If you add all those together it equals 24.94 leaving 6 cents in change

4.50 + 4.00 + 7.75 + 2.75 + 5.94 = 24.94$