Answer
The minimum pulling force is $308.3N$.
Work Step by Step
As we can see in the photo below, in (a), the pulling force $\vec{P}$ carried out at the head of the clown gets translated to the rope tied to his feet into another force $\vec{P}$ there.
In diagram (b), this pulling force $\vec{P}$, to be able to yank the clown's feet out, has to overcome the maximum static frictional force $f_s^{max}$.
Therefore, $$P_{min}=f_s^{max}=\mu_sF_N$$
The normal force $F_N$ is supported here by $P$ and balance the weight of the clown, as shown in photo (b). That means $F_N=mg-P$
$$P_{min}=\mu_s(mg-P_{min})$$ $$P_{min}=0.53(890-P_{min})=471.7-0.53P_{min}$$ $$P_{min}=308.3N$$
