The number of cubic yards of dirt, $\displaystyle {D}$, needed to cover a garden with area $\displaystyle {a}$ square feet is given by $\displaystyle {D}={g{{\left({a}\right)}}}$

a. A garden with area 7000 $\displaystyle {\left({f}{t}\right)}^{{2}}$ requires 60 cubic yards of dirt. Express this information as an equation, in terms of the function g.



b. Explain the meaning of $\displaystyle {g{{\left({90}\right)}}}={4}$ in a complete sentences.