An RC $($f$\text{'}$c$21$ MPa $)$ rectangular beam has a width of $260$mm and an overall depth of $470$mm$.$ The concrete clear cover is $40$mm$,$ the stirrup size is $10$mm$,$ and the size of the longitudinal reinforcement is $20$mm$.$ Steel yield strength for both the flexure and shear bars is $415$MPa. Determine the design shear strength $($kN$)$ of the section if the spacing of the shear reinforcement is $50$mm$.$