Assignment:
Two mountain bikers started from the ranger station in Rocky Mountain National Park traveling in the same direction on Trail Ridge Road. The first biker left 1 hour earlier than the second and traveled 10 miles/hour. The second biker left later and traveled 15 miles/hour. By 4:00 pm, the second biker had passed the first and was 5 miles ahead of the first biker. What time did the first biker leave the ranger station?
Provide complete and step by step solution for the question and show calculations and use formulas.