The firm uses3units of capital(the Fixed Input),and therent on capitalis$200per unit per day. The firm must hire between1to5units of labor(the Variable Input), and thecost of laboris$60per worker per day. Depending on how much labor the firm hires, output (Total Product) is one of the following:

q₁= 1

q₂= 3

q₃= 8

q₄= 12

q₅= 15

What is the Marginal Cost (MC) when 4 units of labor are used?(Do not include the dollar sign $ in your answer)