Answer
$155cm^3$
Work Step by Step
We can determine the required volume of the gas as follows:
$V^{\prime}=\frac{p_a}{p_a+\rho gh}V$
We plug in the known values to obtain:
$V^{\prime}=\frac{101300}{101300+(1000)(9.8)(3)}$
This simplifies to:
$V^{\prime}=155cm^3$
