$5.$ A long simply supported box beam is assembled using plan nailed as shown using diameter nails that can resist a maximum shea stress of each. a$)$ Determine the spacing of the nails along the beam required in order to resist a shear force when the beam is subjected to bending if $.($S $,$ use b$)$ Calculate the maximum bending stress at the bottom of the beam if $.$A $10m$ long simply supported box beam is assembled using $400100$ planks nailed as shown using $12mm$ diameter nails that can resist a maximum shear stress of $300$MPa each.

a$)$ Determine the spacing of the nails along the beam required in order to resist a shear force $V_{\text{m}\text{a}\text{x}}=600kN$ when the beam is subjected to bending if $Ix=6,330{10}^{6}m{m}^4.,$ use $70mm.$

b$)$ Calculate the maximum bending stress at the bottom of the beam if $M_{\text{m}\text{a}\text{x}}=2,300kNm.($fc $($:cax$=109$MPa$\}$