URGENT MATH 10 QUESTION PLS!

Alex bought 144 bagels for $80. His profit was $75 once he had sold 100 bagels.
Which equation below represents Alex’s profit P, as a function of the number sold, n?
1)P = −0.05n + 80
2) P = 0.05n − 80
3) P = 0.75n
4)P = 1.55n − 80
Which one and why? Please explain in detail :)

So if his profit was 75 after 100 bagels, that means he had sold 80+75 = $155 of them.

$155 / 100 = $1.55 per bagel.

So profit = 1.55 times number of bagels, less cost of 80.
P=1.55n -80

Answer 4

We are given that his profit was $75 after selling 100 bagels. His costs were
$80, so profit 75 = 100*p - 80 where p is the price for one bagel. So
155 = 100*p ---> p = $1.55. Thus the profit function will be

P(n) = 1.55*n - 80, or answer 4).

Note that P(100) = 1.55*100 - 80 = $75 as expected. Alex hits break even
when 0 = 1.55*n - 80 ---> n = 80/1.55 = 51.6, so since n must an integer
we would need to round up to 52, i.e., he was making a profit after selling
52 bagels. Just in case you wanted to know. :)

Profit = Revenue - Cost
75 = 100S - 80 where S = selling price
S = 155/100 = $1.55
P = 1.55n - 80
Answer 4)