Answer
a) Less
b) $Err_{\%}=-2\times10^{-4}\%$
c) $Err_{\%}=-0.603\%$
Work Step by Step
a) $P_a=P_v+\rho gh$
The pressure shown by the barometer is equal to the sum of the vapor pressure and the pressure exerted by mercury. If we are ignoring the vapor pressure of $0.0015mm-Hg$ the measured value will be slightly smaller than the actual atmospheric pressure.
$P_{a m}=P_{aa}-P_v$
$0.0015mmHg\times\frac{133.3Pa}{mmHg}=0.19995Pa$
b) $Err=\frac{P_{aa}-P_v-P_{aa}}{P_{aa}}=\frac{-P_v}{P_{aa}}=\frac{0.19995Pa}{101325Pa}=-2\times10^{-6}$
$Err_{\%}=-2\times10^{-4}\%$
c) $Err_{\%}=-\frac{P_v}{P_{aa}}\times100\%=-\frac{611Pa}{101325Pa}\times100\%=-0.603\%$
