`1` mole of an ideal diatomic gas undergoes a reversible polytropic process `(PV^(2)="constant")`. The gas expand from initial volume of `1` litre and temp `300 K` to final volume `3` lit. Claculate change in internal energy (approx).
A. `-40 KJ`
B. `-4.2 KJ`
C. `-4.4 KJ`
D. `-4.6 KJ`