Question

Two long wires, each carrying a current of 9.6A, lie a distance of 49cm from each other. What is the magnetic force per unit length exerted by one on the other.

Answer is in N

Answer 1

You do not specify the directions so we can only say the magnitude
49 cm = 0.49 meters
F = uo i*i / 2 pi d) = uo i^2/(2 pi d) = (4 pi*10^-7) 9.6^2 / (2 pi * .49)

Answer 2

from the Biot-Savart law, the magnetic field from one wire is
B=mu*I/(2PI*d) where I is 9.6, d = .49m, you know PI and mu
now the force jper unit length on the wire which cuts that magnetic field is
Force/length=I*B=9.6*B, where B is above.