n moles of an ideal monoatomic gas undergoes a process from 1 →4 as shown in the figure. T1=500 K,  T4=200 K, P1=105  Pa and P2=4×105Pa. In state 3, 3V3=V1. The change in internal energy from state 3 to state 4 is x Joules. The value of ‘x’ is (Take no. of moles n = 1/R, where R = gas constant)

P−4×105T−500=−3×105−300⇒P=103T−105⇒nRTV=103T−105As  n=1R​⇒1V=103−105T  straight line from 2 to 4​At point 1 , V1=nRT1P1=500105m3 ​Given : 3V3=V1​⇒V3=V13=5003×105m3At point 3,1V3=103−105T3​⇒3×105500=1000−105T3​⇒600=1000-105T3⇒T3=250K​Change in internal energy from state 3 to state 4 , △U=nCVT4−T3=32×200−250 =−75J