Two parallel long wires carry currents of equal strength. How will the force of interaction of wires per unit

Two parallel long wires carry currents of equal strength. How will the force of interaction of wires per unit length change if the distance between the wires changes from 80 cm to 20 cm?

The force of interaction between two straight conductors can be calculated by the formula:
F = μ0 * μ * I1 * I2 * ∆L / (2Π * d), where μ0 is the magnetic constant, μ is the relative permeability, I1 is the current in the first conductor, I2 is the current in the second conductor, ∆L is length of the section of conductors, d is the distance between the conductors (m).
Before changing the distance between conductors:
F1 = μ0 * μ * I1 * I2 * ∆L / (2Π * d1), where d1 = 80 cm = 0.8 m.
After changing the distance between the conductors:
F2 = μ0 * μ * I1 * I2 * ∆L / (2Π * d2), where d2 = 20 cm = 0.2 m.
F2 / F1 = (μ0 * μ * I1 * I2 * ∆L / (2Π * d2)) / (μ0 * μ * I1 * I2 * ∆L / (2Π * d1)) = d1 / d2 = 0.8 / 0.2 = 4.
Answer: The strength of interaction will increase by 4 times.