A fluid moves at steady$-$state through a $24"$ inner diameter horizontal pipe. From a point $3$ feet downstream from the pipe entrance, the fluid moves with average velocity given by

vec$(V)(r,,z)=20**(1-r{)}^{0\mathrm{.}1}$hat$(k)$ feet $\frac{?}{sec}$ for $0r1ft$ and $3z20ft$