Errors and uncertainties — practice question

The liquid volume $V$ that passes in time $t$ through a pipe of radius $r$ is described by $\frac{V}{t} = \frac{\pi P r^4}{8 C l}$, where $P$ is the pressure difference across the two ends of a pipe of length $l$, and $C$ is determined by the liquid’s frictional effects. An experiment is carried out in order to find $C$. The readings obtained are shown in Fig. 1.1.