For Problems $8-21$ through $8-30,$ assume that the indi$-$ cated shape is the cross section of a beam made from wood having an allowable shearing stress of $70$ psi, which is that of Grade No$.2$ southern pine listed in Appendix A$-15.$ Compute the maximum allowable shearing force for each shape. Use the general shear formula.

$8-21.$

Use a standard $2$x$4$ wooden beam with the long dimension vertical.