গণিত প্রশ্ন

A turtle and a rabbit engage in a footrace over a distance of 4.00 km. The rabbit runs 0.500 km and the stops for a 90.0 min nap. Upon awakening, he remembers the race and runs twice as fast. Finishing the course in a total time of 1.75 h, the rabbit wins the race. What was his average speed before he stopped for a nap!