Answer
a) $h=1.06m$
b) $90.7N$
Work Step by Step
(a) We can find the required height as follows:
$f_{max}=\mu_smg=(0.571)(16.2)(9.81)=90.7N$
Now $\Sigma \tau=(\frac{1}{2})mg-hF=0$
This simplifies to:
$h=\frac{mgL}{2F}$
We plug in the known values to obtain:
$h=\frac{(16.2)(9.81)(1.21)}{2)(90.7)}$
$h=1.06m$
(b) We know that the required force is $90.7N$ because it cannot be greater than the maximum static friction.
