the volume of the prism is simply the area of any of the sides times the length, so in this case the shaded area times 4.
[tex]\stackrel{area}{\left( 2\frac{1}{8} \right)}(\stackrel{length}{4})\implies \left( \cfrac{17}{8} \right)(4)\implies \cfrac{17}{2}\implies 8.5~units^3[/tex]
