Answer
See explanation.
Work Step by Step
Assume 80 beats/minute. This equates to 4800 beats each hour, 115200 in a 24-hour day, 42048000 in a 365-day year, and $N=3363840000=3.4\times10^9$ beats in an 80-year lifetime.
The volume of blood pumped per beat is given as $50\;cm^3$.
The total volume pumped is $(N)(50\;cm^3)(\frac{gallon}{3785\;cm^3})=4.4\times10^{7}$ gallons.
