Answer
$(a)\space 16.7\space J $
$(b)\space 1.4\space W$
Work Step by Step
(a) Here we use the equation $W=mgh$ to find the work done in lifting 1L of blood from the foot to the head.
$W=mgh$
Let's plug known values into this equation.
$W=1\space kg\times9.8\space m/s^{2}\times1.7\space m$
$W=16.7\space J$
(b) Let's take the work done by the heart = P, We can write,
$p=\frac{Total\space work\space done}{Total\space time}$
Let's plug known values into this equation.
$P=5\times\frac{16.7\space J}{1\space min}(\frac{1\space min}{60\space s})=1.4\space W$
