Tyler's spaceship leaves Earth and travels at a constant speed of 3c/5, except for a negligible time period at the middle of its journey when it turns around to return to Earth as well as negligible acceleration time periods at the start and end of its journey. When Tyler returns to Earth, he finds that 10 years have elapsed according to clocks on Earth. In years to one significant figure, how much time has elapsed according to the clocks on Tyler's spaceship?