If three moles of an ideal gas at 300 K expand isothermally from 30 dm^3 to 45 dm^3 against a constant opposing pressure of 80 kPa, then the amount…

If three moles of an ideal gas at $\displaystyle 300$ K expand isothermally from $\displaystyle 30 \mathrm{dm}^3$ to $\displaystyle 45 \mathrm{dm}^3$ against a constant opposing pressure of $\displaystyle 80$ kPa , then the amount of heat transferred is $\displaystyle \_\_\_\_$ J.