determine the design angle ϕ ( 0 ° ≤ ϕ ≤ 90 ° ) ϕ(0°≤ϕ≤90°) between members ab and ac so that the 400-lb horizontal force has a component of 600 lb which acts up to the right, in the direction from b toward a. also calculate the magnitude of the force component along ac. take