Since four friends should make a profit of $400 each, the total undivided profit should be $1600. Profit (P) is the difference between the total revenue (R) and the total cost (C).
P = R - C ; R = P + C
Substituting the known values,
R = $1600 + $525 = $2125
Thus, the total income that the friends should earn is $2125.
