Answer
In this question we have given,
Height of plane, h1=2000m
Height at which charge concentration is 40C, h2=3000m
Height at which charge concentration is -40C, h3=1000m
charge concentaration, q1=40C
charge concentaration, q2=-40C
let the charge concentrations at height h2 and h3 as point charges
Now we will first find the electric feild on plane due to positive charge q1=40

Here k=8.98755*10^9N.m^2/C^2
q1=40C
put values of k, q1 , h1 and h2 in equation 1
\\
V/m[/tex]
similarly electric feild due to negative charge q2=-40
\\

Total electric feild E at the aircraft is given as
...............(2)
Put values of E1 and E2 in equation2

therefore s Total electric feild E at the aircraft is E= 719004V/m