Answer
The average power of the flywheel is $P=-\frac{-29.9J}{1.5s}=19.9 Watt$
Work Step by Step
The average power of the flywheel can be calculated from the amount of work working on the flywheel and the time it's due.
The power of the flywheel is the power it uses to resist the amount of work working on it, so we need to include a minus sign to the equation:
$P=-\frac{W}{t}$
from the previous section of the problem (see P.39c) we have $W=-29.9J$
$P=-\frac{-29.9J}{1.5s}=19.9 Watt$
