Xin's X-Ray business operates in a perfectly competitive market. The equilibrium price in the market for X-rays is $50. Xin's total costs of supplying different quantities of X-Rays are: Qty Total Cost 0 $1000 1 $1020 2 $1060 3 $1100 4 $1180 5 $1280 6 $1400 7 $1540 8 $1700 9 $1880 10 $2080 What is the profit maximising quantity of X-Rays for Xin to supply? Group of answer choices Zero 10 5 3 2