Question 969468
D is correct.

Cost equation is y=10,000 + 10x  where x is the number of pair of shoes.

Revenue equation is y=30 x

Set them equal   
30x=10000 + 10x
20x=10,000
x=500 pair of shoes.
Break even point at $500*30=$15,000  OR 10,000 + 500*10=$15,000



{{{graph (300,200,-50,1000,-100, 20000,10x+10000,30x)}}}  This shows the break even point at $15,000.  Green line is revenue; Red line is cost.