Mikey decides he wants to go for a run at 3:30 pm. He knows that the burger joint is 4.2 km away, the high school is 3.29 km away and the bank is 1.96 km away. He decides he will set out for the high school to see if any of his friends are there. After running to the high school and back, he looks at his watch and it's now 5:15 pm. What was the average speed of Mikey on his run?