Answer
Please see the work below.
Work Step by Step
We know that
$E=(420Kcal)(\frac{4184J}{1 Kcal})=1757280J$
The power is given as
$P=\frac{E}{t}$
This can be rearranged as:
$t=\frac{E}{P}$
We plug in the known values to obtain:
$t=\frac{1757280}{200}=8786.4s=2.44h$
Now we can find the distance as:
$d=vt$
We plug in the known values to obtain:
$d=(3)(2.44)$
$d=7.3km$
