$(3)$ There is a rectangular plate with a side length of $2$a in x$-$direction and $2$b in y $-$

direction. The plate has a uniformly distributed surface charge density $\backslash$sigma $.$

$($a$)$ Find the potential at P$(0,0,$z$\_(0))$ due to

this charged plate.

$($b$)$ Find the electric field at P$(0,0,$z$\_(0))$

due to this charged plate.

Please answer both parts of the question in detail