<PRE><B>Question 254415</B>
P = (80+x)(200-2x)
P = is a parabola that opens down. This means there is a maximum profit somewhere.
P = -2x^2 + 40x + 16000
We can find the vertex using -b/2a as
-b/2a = (-40/-4) = 10
Put in x = 10 and we get
P = 90*180 = 16200
Since the number of passengers increases, we get 80+10 = 90.

90 passengers gives us a profit of $16,200</PRE>