The Correct Answer is (C) —
This problem is asking you to find the profit for selling one barrel of oil. There are different costs for each step in the process, and some steps occur multiple times, so in order to solve without losing track of anything we can write an algebraic expression. The revenue for the sale, r, is the amount the barrel is sold for, or $93. The costs are: $51 for extraction, e, two transportation steps, t, at $6 each, and three processing steps, p, at $9 each. So we can represent the whole formula for profits as: p = r - e - 2t -3p. We can now plug in the values for each of our variable and solve: p = (93) - (51) - 2(6) - 3(9) = 93 - 51 - 12 - 27 = 42 - 12 - 27 = 30 - 27 = 3, which is answer option (C).