Megan is jealous of her older sister's a by b inch Zac Efron poster, so she cuts out a rectangle around his face, which has dimensions (a/2)-5 by (b/3)-8, and steals it. Megan's older sister decides she's over Zac Efron anyways, and uses the rest of the paper as wrapping paper. She wraps a 12-inch cube, wasting no paper, and has 7 square inches leftover. If a and b are integers and b>a, and the difference between the length and width of the poster is less than 50, find the dimensions of the poster. Express your answer as the ordered pair (a,b).