Please help on #7 !!!

Saline iv fluid bags cost $64.20 for 24, 1000 ml bags from one supplier. a new supplier sells 500 ml bags for $2 each. the hospital uses about 10,000, 1000 ml bags each month. nurses report that about half of the bags are more than half full when they are discarded. if you are going to use only one supplier, which size bag provides the best deal, and how much will you save each month? compare the cost of the new supplier to the current one.

You have 138.72 in your saving account u take out 45.23 and 18.00 you deposit 75.85 into your account

Use the elimination method to solve the systems of equations.choose the correct ordered pair. 7x+4y=39