(13-0.25x4)(12+4x4)=2,464
(13-0.25x5)(12+4x5)=3,845
(13-0.25x6)(12+4x6)=2,845
so your answer is 3,845 because if Hirome sells them for $11.75 he makes $3845 if Hirome sold them for $11.50 he makes $2845.80 and if he sold them for $12.00 he would make $2464.00