Amilling operation was used to remove a portion of a solid bar of square cross section. if a = 30 mm, d = 20 mm, and σall = 60 mpa, determine (a) the magnitude p of the largest forces that can be safely applied at the center of the ends of the bar if the stress concentration at the fillet is ignored, and (b) the max value of p if the stress concentration is considered (idealize your section with d=d and pretend fig 4.24 of b& j applies when estimating k).