The area of a trapezoid with bases a & b with height h is given by $\displaystyle {A}=\frac{{1}}{{2}}{h}{\left({a}+{b}\right)}$.

If a contractor needs to lay a cement slab designed as a trapezoid with bases of $\displaystyle {1}\frac{{2}}{{7}}$ yards and $\displaystyle {2}\frac{{1}}{{4}}$ yards with a height of $\displaystyle {1}\frac{{1}}{{3}}$ yards, what is the area of the slab?

Enter number only.