Isothermal Expansion and Change in Internal Energy

In a closed system, a gas undergoes an isothermal expansion at a temperature of 300 K. The initial volume of the gas is 5.0 L and the external pressure surrounding the gas is 1.2 atm. The gas does 150 J of work during this expansion. Given that the ideal gas constant R is 0.0821 L·atm/(K·mol), calculate the change in internal energy (ΔU) for the gas during this process. Select the correct option for ΔU.