A 12-story office building is 120 ft tall with plan dimensions of 120 × 80 ft. the structure is of conventional curtain wall construction with all windows fixed in place. there are double vestibule-type doors on all four sides. under winter design conditions, a wind of 15 mph blows normal to one of the long dimensions. estimate the pressure differences for all walls for the first and twelfth floors. consider only wind and stack effects. the indoor–outdoor temperature difference is 60 f.