Telco makes fuse boxes for cars. After variable expenses are deducted from the selling price for each fuse box, the remaining amount is $5. If total fixed costs for Telco are $21,000 and they want to make a profit of $10,000, how many fuse boxes must they sell?
4,200 fuse boxes
6,200 fuse boxes
155,000 fuse boxes
2,000 fuse boxes