Question 34981
A more direct aopproach would be to set up a ratio on sales to profit thus

(70,000-50,000)/(9,000-6,000) or 20,000/3000 or for every 20,000 in sales the 

co. makes 3,000 profit so for no profit they have to loose 6,000 profit from 

sales of 50,000  thus they would have to loose 2*20,000 sales or 40,000

50,000-40,000=10,000 sales would equal 0 profit.