Determine the maximum combined loads using the recommended aisc expression for lrfd: (a) d=100 psf, l=70 psf, r= 12 psf, lr=20 psf, and s=30 psf. (b) d=12,000 lb, w= 52,000 lb (load induced by wind may be positive or negative depending on wind direction. you should consider both) (c) d=9000 lb, l=5000 lb, lr=2500 lb, e=6500 lb (earthquake load may be positive or negative depending on the earthquake direction)