Answer
$0.921$
Work Step by Step
We know that
$PV=nRT$
$\implies \frac{nT}{V}=\frac{P}{R}=constant$
$\implies \frac{n_1T_1}{V_1}=\frac{n_2T_2}{V_2}$
This can be rearranged as:
$\frac{n_2}{n_1}=\frac{T_1V_2}{T_2V_1}$
We plug in the known values to obtain:
$\frac{n_2}{n_1}=\frac{294K}{335K}\times \frac{4.20\times 10^3m^3}{4.00\times 10^3m^3}=0.921$
