We see that the slope intercept is y = 8x - 20. So if we substitute x with 2, because x represents the amount of necklaces sold and we are analyzing her net profit after selling 2 necklaces, that gives us y = 8(2) - 20. Which simplifies to y = -4. So by the time Jocelyn sells 2 necklaces, her net profit will be at -4.
, you get 
, and the integral becomes
