The internal energy of an ideal gas follows the equation u=3.5 pv+ k, where k is a constant. the gas expands from an initial volume of 0.25 m to a final volume

The internal energy of an ideal gas follows the equation U=3.5 PV+ k, where k is a constant. The gas expands from an initial volume of 0.25 m to a final volume of 0.86 m'. If the initial pressure is 5Nm, the change in internal energy (in Joules) is (given PV= constant)