R(p) = -2.5p2 + 550p
The graph of f(x) = Ax2 + Bx + C (A≠0) is a parabola. When A < 0, the graph has maximum value when x = -B/(2A).
So, R(p) has maximum value when p = -550/(2(-2.5)) = $110
Maximum revenue = R(110) = -2.5(110)2 + 550(110) = $30,250