#### Answer

The work done on the gas is -80 J

#### Work Step by Step

We can calculate the work done on the gas as:
$W = -P\Delta V$
$W = -P ~(V_f-V_i)$
$W = -(4.00\times 10^5~Pa)(300\times 10^{-6}~m^3-100\times 10^{-6}~m^3)$
$W = -80~J$
The work done on the gas is thus -80 J.