Answer
$a.\quad\approx 1636$ hours
$b.\quad\approx 31$ hours/week
Work Step by Step
$ a.\quad$
1 billion = $10^{9}$
1 milion = $10^{6}$
$\displaystyle \frac{342\times 10^{9}}{209\times 10^{6}}=\frac{342}{209}\times 10^{9-6\quad ... dividing \ powers \ with \ the \ same \ base}$
$= 1.6363636\times 10^{3}$
$\approx 1636$ hours
$ b.\quad$
There are 52 weeks in a year. Divide the result of (a) with 52
$\displaystyle \frac{1.6363636\times 10^{3}}{52}\approx 31.468531$
$\approx 31$ hours/week
