The $159-lb$ exerciser is repeated from Chapter $3.$ The tension $T=26lb$ is developed against an exercise machine $($not shown$)$ as he is about to begin a biceps curl. Determine the minimum coefficient of static friction which must exist between his shoes and the floor if he is not to slip. The center of gravity of the exerciser is at point $G.$

Assume $a=12in.b=,12in.c=,14in.d=,58in.,$ and $=17.$

Answer: ${}_s=$