At point ##P(0,0'03,0'04)## the field caused by the sphere is added to the field caused by the plane.
First, ##E_\sigma##
$$E_\sigma=\dfrac{\sigma}{2\varepsilon_0}=\dfrac{0,2\cdot 10^{-6}}{2\varepsilon_0}=11299,44\, \textrm{V}/\textrm{m}$$
Then, ##E_0##: Because ##r<R##...