Cardiac output = Stroke volume $\times$ Heart beats per minute.
Cardiac output is the amount of blood pumped by heart per
minute. Human heart beats for about 72 times per minute.
Cardiac output is about 5L.
$\therefore $ Stroke volume $ = \frac{\text{Cardiac output}}{\text{Heart beats per minute}} $
$ = \frac{5040}{72} = 70\,ml$