A rectangular reinforced concrete beam with a width of $200mm$ and a total depth of $400mm$

is reinforced with D$16$mm main bars and D$10$ closed stirrups for shear reinforcements. If it

has a span of $6m$ and is loaded with unfactored $10K\frac{N}{m}$ distributed live load and unfactored

$5K\frac{N}{m}$ distributed dead load $($including its own weight$),$ solve for the required spacing of the

stirrups. $F^{\text{'}}c=21$MPa, fyt$=275$ MPa. Use concrete cover of $40mm.$