City X and City Y are 420 km apart. At 3.45 p.m., Joni is travelling at a uniform speed left City X for City Y while Ben set off from City Y to City X along the same road at a uniform speed, which was 12 km/h slower than that of Joni. The two met at 6.45 p.m.
- Find the speed of Joni.
- If Ben continued to travel at the same speed, how long would it take to reach its destination after the two met? Express the answer in mixed number.