253-254 Equivalent single force to replace a force and a couple

Problem 253
In Fig. P-253 a system of forces reduces to downward vertical force 400 lb through A plus a counterclockwise couple of 800 lb·ft. Determine the single force that will produce an equivalent effect.
 

Problem 254
Rework Prob. 253 if the system reduces to a leftward horizontal force of 300 lb through point A plus a clockwise couple of 750 lb·ft.