Answer
(a) $332K$
(b) $555KJ$
Work Step by Step
(a) We know that
$PV=nRT$
This can be rearranged as:
$T=\frac{PV}{nR}$
As the process is isothermal so $T_i=T_f=T$
We plug in the known values to obtain:
$T=\frac{100\times 10^3(4.00)}{145(8.31)}$
$T=332K$
(b) As $W=nRT\ln(\frac{V_f}{V_i})$
$\implies W=P_iV_i\ln(\frac{V_f}{V_i})$
We plug in the known values to obtain:
$W=400(1.00)(\frac{4.00}{1.00})=555KJ$