In business economics, the "efficient" quantity is the one that sets the marginal benefit equal to the marginal cost.

MD = 2+5x = MB = 34-3x

2 + 8x = 34 (add 3x to both sides)

8x = 32 (subtract 2 from both sides)

x = 4 (divide both sides by 8)

MD = 2+5x = MB = 34-3x

2 + 8x = 34 (add 3x to both sides)

8x = 32 (subtract 2 from both sides)

x = 4 (divide both sides by 8)