$2\mathrm{.}6\mathrm{.}26$ Consider the cistern manometer shown in Fig. P$2\mathrm{.}6\mathrm{.}26.$ The

scale is set up on the basis that the cistern area $A_1$ is infinite. However,

$A_1$ is actually $50$ times the internal cross$-$sectional area $A_2$ of the

inclined tube. Find the percentage error $($based on the scale reading$)$

involved in using this scale.

FIGURE P$2\mathrm{.}6\mathrm{.}26$