One mole of an ideal monoatomic gas expands isothermally against constant external pressure of `1 atm` from intial volume of `1L` to a state where its final pressure becomes equal to external pressure. If initial temperature of gas in `300 K` then total entropy change of system in the above process is:
`[R=0.0082L atm mol^(-1)K^(-1)=8.3J mol^(-1)K^(-1)]`
A. `0`
B. `R l n(24.6)`
C. `R l n(2490)`
D. `3//2R l n(24.6)`