Each person's share of baseball cards if 4 people share c cards equally

Find the given elements if matrix d:

Can someone check if i did this correct. it’s number 4 if you’re wondering.

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.