Answer:
t = 10.5 minutes
Explanation:
Curves on the graph show the distance covered by two runners during the first 21 minutes of a race.
These curves intersect each other at a point which shows a common location of both the runners on the graph.
This common point is at the mid of t = 9 and 12 seconds
Therefore, time at which both the runners passes the other will be,
t =

= 9 + 1.5
= 10.5 minutes