$12\mathrm{.}72$ A pitot ube having a coefficient of unity is inserted in the exact center of a long, smooth tube of $25\mathrm{.}0$mmID in which crude oil $($sp$.$ gr$.=0\mathrm{.}9$ and $=16\mathrm{.}7$ centipoises$)$ is flowing. Determine the average velocity in the tube if the velocity pressure is $100$ mm of water.

a$.0\mathrm{.}56\frac{m}{sec}$

b$.0\mathrm{.}65\frac{m}{sec}$

c$.0\mathrm{.}74\frac{m}{sec}$

d$.0\mathrm{.}82\frac{m}{sec}$