Answer:

Step-by-step explanation:
From the question we are told that
The electric filed is
Generally according to Gauss law
=>

Given that the electric field is pointing downward , the equation become

Here
is the excess charge on the surface of the earth
is the surface area of the of the earth which is mathematically represented as

Where r is the radius of the earth which has a value

substituting values


So

Here
s the permitivity of free space with value

substituting values

