It is known that all element thicknesses shown in the figure are $5mm.$ a$)$ How many $mm$ should the distance $b$ be for point o to be the shear center of the section?

b$)$ Draw the shear stress distribution graph of the section for the case where a shear force of $320kn$ acts on the shear center of the section. $($all dimensions shown on the section are in $mm.$

c$)$ If the section is produced from steel with a yield stress of $500$mpa, check whether it can safely carry the stresses.