Answer:
Let x=number of $0.25 increases, so the equation for revenue=price*number of tickets or people) becomes
Revenue=($3.00+$0.25x)(400-20x)
where ($3.00+$0.25x) :increase in price
and
(400-10x) : decrease in number of people
Expanding Revenue
Revenue[R]=1200-60x+100x-5x²:1200+40x-5x²
Taking the derivative of R and set it equal to 0:
R'=0+40-10x=40-10x
we have
R'=0
40-10x=0
x=40/10
x=4
So the ticket price is $3.00+$0.25*4=$4
The number of people will attend is 400-20*4=$320
At $320 ticket price will the revenue be maximized.