Two wood box beams (beams A and B) have the same outside dimensions (200mm x 360mm) and

Question:

Two wood box beams (beams A and B) have the same outside dimensions (200mm x 360mm) and the same thickness (t = 20mm) throughout, as shown |in the figure on the next page. Both beams are formed by nailing, with each nail having an allowable shear load of 250 N. The beams are designed for a shear force B = 3.2kN.
(a) What is the maximum longitudinal spacing SA for the nails in beam A?
(b) What is the maximum longitudinal spacing SB for the nails in beam B?
(c) Which beam is more efficient in resisting the shear force?