#### Answer

The total work done by the gas during these two processes is $~101~J$

#### Work Step by Step

When $\Delta V = 0$, the work done is zero. Therefore, the work done from A to B is zero.
The work done by the gas during a constant pressure process is $P\Delta V$. We can find the work done by the gas from B to C:
$W = P~\Delta V$
$W = (1~atm)(2~L-1~L)$
$W = (1~atm)(1~L)$
$W = (1~atm)(1.01\times 10^5~Pa/atm)(1~L)(10^{-3}~m^3/L)$
$W = 101~J$
The total work done by the gas during these two processes is $~101~J$