Suppose $u$ is a solution of
$\nabla^2 u = 0$
inside the unit circle for the boundary condition that $u$ is equal to 3 for a quarter of the circle, and 6 for the remaining 3 quarters of the circle. Find $u$ at the origin:

$u(0,0) = {}$

Use what you know about the Poisson formula and your intuition.

help (numbers)