The forge produces iron (x) with the cost function C_x(x)=20x^2, while it can sell the iron at the competitive price $16. The farmer produces apples (y) with the cost function C_y(x, y)=3y^2+2xy, while it can sell the apples at the competitive price $11. If the government wants to tax the forge to incentivize it to produce the socially optimal amount, how much should the government tax the forge per unit of iron produced? Round your answer to 2 decimal points.