We can find this point as the intersection point between the two profits functions:
From this expression we know that the companies made the same profit when they made no units (x=0) or they made 200 units (x=200). We will ignore x=0 as a solution because it is trivial.
Then, the profit for 200 units can be calculated with any of the two profit functions, as they have the same value for x=200:
Answer: both factories will have the same profit when they manufacture 200 chairs because each factory earns a profit of $1500 {fourth option].