A $12"$ wide beam below supports two equal concentrated loads at it's two third points. The two loads are factored

$($combined$)$ and have a magnitude of $90$ kips. Neglect the self$-$weight of the beam and use normal weight$($s$)$: $f{c}^{\text{'}}=$

$5,000,$ and fyt $=60,000.$ The effective depth of the tension reinforcement is $21\mathrm{.}5in.$

a$.$ Draw a shear diagram of the beam under the two concentrated loads.

b$.$ On the shear diagram $($a$),$ Mark the regions where shear reinforcement is NOT required.

c$.$ If the No$.4$ double$-$leg stirrups are used as shear reinforcement, then determine the spacing of the stirrups

in the regions where shear reinforcement IS required, and check the design based on minimum shear

reinforcement and maximum spacing of stirrups.