A dealer wishes to produce 300 gallons of oil worth 40¢ a quart. He will mix oil that is worth 36¢ a quart with oil that is worth 52¢ a quart, and needs to figure out how many quarts of each he needs.

If x represents the number of quarts of 36 cent oil, which of the following equations could be used to solve this problem?

0.36x + 0.52x = 0.40(1200)
0.36x + 0.52(1200 - x) = 0.40(1200)
0.36x + 0.52(300 - x) = 0.40(300)