The cost function to make n hats is C(n) = 42*n + 243 dollars. The revenue function is R(n) = 69*n dollars. The break event equation/inequality is R(n) >= C(n), or 69*n >= 243 + 42*n. Simplify and solve for n: (69-42)*n >= 243 27n >= 243 ===============> n >= 243/27 = 9. ANSWER. 9 hats.