4. A cantilever beam of length L = 10 ft, and s̟ = 0.1 ft, is required to support a concentrated load P =500 lb, and sp = 25 lb,

at its free end. The beam is made of a material with an yield strength ỹ =75 ksi, and s, = 5 ksi. If the probability of failure has to be less than 0.5%, what is minimum width ċ of a square cross section to be used? Assume s̟ = 0.025c.