Answer
given,
opera house ticket = $50
attendance = 4000 persons
now,
opera house ticket = $52
attendance = 3800 person
assuming these are the points on the demand curve
(x, p) = (4000,50) and (x,p) = (3800,52)
using point slope formula




R(x) = x . p




at


x = 4500

hence at x =4500 the revenue is maximum
for maximum revenue ticket price will be

p = $45