For the large square surface in the top you do 12*15=180 and there are two large squares faces so you multiply 180 by 2 which equals 360 then you find the small rectangle faces: 5*15=75 and multiply by 2 Bc there are 2 faces like that so it would be 75*2=150 then for the last faces you do 12*5= 60 *2= 120 at the end I add all of the faces up, 360+150+120=630
