Assuming that their heart will not increase speed or decrease speed of beating
Caleb: 700 times/ 10 minutes = 70 times/minute, hence in 5 minutes his heart beats 70 * 5 = 350 times
Steve: 536 times/ 8 minutes = 67 times/minute, hence in 5 minutes his heart beats 67 * 5 = 335 times
350-335 = 15 times
Caleb's heart beat 15 times more than Steve's in 5 minutes
