Hello!
your answer is: 2 minutes, 49 seconds, and 800 milliseconds
to get this, divide 204 by 72. that gives you the amount of minutes the heart was beating, which is 2.83 minutes
then, multiply 2.83 by 60 to get the seconds
you have 169.8 seconds.
2 minutes is equal to 120 seconds, so subtract that from 169.8
that leaves 49.8 seconds
.8 seconds is equal to 800 milliseconds
so put it all together and you have: 2 minutes, 49 seconds, and 800 milliseconds
I hope this helps, and have a nice day!