Estimating magnitude PHYSICS QUESTION!?

A square metal plate of edge length 8.9 cm and negligible thickness has a total charge of 8.8 x 10-6 C. (a) Estimate the magnitude E of the electric field just off the center of the plate (at, say, a distance of 0.54 mm from the center) by uming that the charge is spread uniformly over the two faces of the plate. (b) Estimate E at a distance of 25 m (large relative to the plate size) by uming that the plate is a point charge. Give your answers in N/C.