Area & perimeter of l shapes

Name the most appropriate metric unit for each measurement like the mass of cow

Asmall business produces and sells balls. the fixed costs are $20 and each ball costs $4.32 to produce. each ball sells for $8.32. write the equations for the total cost, c, and the revenue, r, then use the graphing method to determine how many balls must be sold to break even.

Hi, can anyone show me how to do this problem? 100 points for this. in advance