$(7).$ An ideal fluid flows through a pipe made of two sections with diameters of $1\mathrm{.}0$ and $3\mathrm{.}0$ inches, respectively. The speed of the fluid flow through the $3\mathrm{.}0-$inch section will be what factor times that through the $1\mathrm{.}0-$inch section?

a$.6\mathrm{.}0$

b$.9\mathrm{.}0$

c$.\frac{1}{3}$

d$.\frac{1}{9}$