Answer
6480 L.
Work Step by Step
Normal pulse rate is 60 beats/min.
$1 day = 24\times60\,mins=1440 \,mins$
So, number of beats in 1 day = $60\times1440=86400$
In 1 beat, the heart pumps 75mL of blood.
So, in 1 day, total blood pumped=$75\times86400\,mL=6480000mL=6480L$