Answer:
Electric field,

Step-by-step explanation:
It is given that,
Electromagnetic force acting on the proton when it is at rest,
(in +x direction)
Speed of proton,

We need to find the magnitude of the electric field. We know that when the charged particle is at rest it experiences electric force which is given by :
F = q E

q is charge on proton

E = 5437500 N/C
or

So, the magnitude of electric field is
. hence, this is the required solution.