$ \Rightarrow \,\,2\,\, = \,\,\frac{{1000\,\, \times \,\,2.5\,\, \times \,\,0.76\,\, \times \,\,1}}{{m\,\, \times \,\,100}}$
$m\, = \,\,12.5\,\, \times \,\,0.76$
$\frac{{{P^0}\, - \,\,{P_s}}}{{{P^0}}}\,\, = \,\,\frac{n}{N}$
$\frac{{760\,\, - \,\,{P_s}}}{{760}}\,\, = \,\,\frac{{2.5}}{{12.5\,\,\, \times \,\,0.76}}\,\, \times \,\,\frac{{18}}{{100}}\,\,\,$
$ \Rightarrow \,\,{P_s}\,\, = \,\,724$