$1\mathrm{.}1$ The box section in Figure Q$1($a$)$ is for a beam made of structural steel. Find the maximum

shear load that the section can carry for a safety factor of $1\mathrm{.}2.$ All dimensions are in mm $.$

$1\mathrm{.}2$ If the beam is fabricated as shown in Figure Q$1($b$)$ using screws with a shear strength of

$950$ N $,$ find the optimum spacing for the screws when the beam carries a maximum shear

load as determined in $1\mathrm{.}2$

For the structural steel, $E=200$GPa,${}_Y=240$MPa,$TY=150$MPa and $v=0\mathrm{.}3.$