A force of 315 N is applied horizontally to a wooden crate in order to displace it 35.0 m across a level floor at a constant velocity.

A force of 315 N is applied horizontally to a wooden crate in order to displace it 35.0 m across a level floor at a constant velocity. As a result of this work the crate's internal energy is increased by an amount equal to 18 percent of the crate's initial internal energy. Calculate the initial internal energy of the crate.