Three boards are nailed together to form the beam shown, which is subjected to a vertical shear. Knowing that the spacing between the nails is s = 75 mm and that the allowable shearing force in each...

Three boards are nailed together to form the beam shown, which is subjected to a vertical shear. Knowing that the spacing between the nails is s = 75 mm and that the allowable shearing force in each nail is 400 N, determine the allowable shear.