Determine the potential difference between points A and B of the electric field of a point charge 4 * 10 ^ -8 C in the air

Determine the potential difference between points A and B of the electric field of a point charge 4 * 10 ^ -8 C in the air if the distance from these points to the charge is 1 and 4 m, respectively.

here is the solution, you need to know the formula, and then you must solve by the formula
φ1 = k * q / r1
φ2 = k * q / r2
k = 9 * 10 ^ 9
φ1 = 9 * 10 * 4 = 360
φ2 = 9 * 10 = 90
Δφ = 360 – 90 = 270