Refer to Figure 13-3. In Figure 13-3, why is the total cost (TC) curve rising?

Figure 13-3 20 000 18 000 TC 16 000 TVC 14 000 (000s of dollars) 12 000 10 000 8000 6 000 Tot 4 000 2 000 TFC 10 15 20 25 30 Output (golf carts per month)