Karan, Charan and Madan run along a straight line with speeds 3 m/s, 7 m/s and 10.5 m/s respectively. Charan starts 15 seconds after Karan. Madan starts 20 seconds after Karan. Charan reaches the finish line 11 seconds after Madan. How long after Charan reaches the finish line does Karan reach the finish line?