If I understood the question correctly, the answer would be 400
The production function describes a boundary or frontier representing the limit of output obtainable from each feasible combination of inputs. The production function also gives information about increasing or decreasing returns to scale and the marginal products of labor and capital.
The answer you are looking for is Y = 2/3X - 5.
To find this, you must fill in the equation Y = MX + B, where Y = -1, M = 2/3, and X = 6. Filling in for those variables, you should get -1 = 2/3(6) + B. Now, you solve for B. Multiply 6 and 2/3 together, by putting 6 over 1 and multiplying straight across. 6 times 2 is 12 and 1 times 3 equals. This will give you 12/3, which simplified, is 4. Then, subtract 4 from both sides to get B = -5. Finally, fill in Y = MX + B, but this time only fill in M (2/3) and B (-5). This making Y = 2/3X - 5 the answer. Here's a graph to show this is the correct answer.
I hope this helps!