The insight bus tour offered to take a group of senior citizen to a lake resort for a fare of $120 per person if 25 person or fewer sign up. If more than 25 person make the trip, each fare will be reduced by $20. The capacity of the bus is 40 people. find the total fare revenue function R(x) if x person make the trip.

answer to check : r(x)= -20x+620x
i need the solution pls anyone :((

The formula must have a typo. If not, you are saying that

r(x) = 600x, or $600 per person.

I suspect that the problem is incorrectly stated. It appears that the $20 discount is only being applied to those people in excess of the 25-passenger price break. That explains the -20x.

I have no idea where that 620 comes from.