An initially stationary box of sand is to be pulled across a floor by means of a cable in which the tension should not exceed $1130$ N$.$ The coefficient of static friction between the box and the floor is $0\mathrm{.}450.($a$)$ What should be the angle between the cable and the horizontal in order to pull the greatest possible amount of sand, and $($b$)$ what is the weight of the sand and box in that situation?