Four charged particles are fixed in place at the corners of a square with side length 1.20 meters. (The square is oriented with its edges aligned north-south and east-west.) The particles each have a charge of 5.0 nC. A proton, free to move, is introduced to 1.10 meters to the east from the center of the square. Address the following questions:

a. What is the electric field (a vector) at the location of the proton?

b. What is the electrostatic force (a vector) on the proton?

c. What is the magnitude of the proton's instantaneous acceleration?

d. If the 4 charges were combined into one particle placed at the center of the original square, would the proton's acceleration at the moment of release be larger or smaller relative to the square case? By how much (by what factor)?