Question 463707
R(x) = (2.5 + 0.10x)(140 - 5x) = {{{-0.5x^2 + 1.5x + 350}}}

revenue attains a maximum when {{{x = (-b)/(2a) = (-1.5)/(2*-0.5) = 1.5}}}.

Hence to maximize revenue each magazine should be priced at 2.5 + 0.10*1.5 = $2.65.