Answer: the new force is 78 times higher that the initial force before made the changes.
Explanation: In order to solve this problem we have to take into account the following expression for the force ( per length ) between currents, which is given by:
F/L=(μo*I1*I2)/(2*π*r) where μo is the magnetic permeability of vaccum and r is the distance between conductors. I1 and I2 are the currents.
Considering that I1 and I2 are increased a factor 2 and 3 , respectively,
Also considering that r is decreased by a factor of 13
The new force per Length is:
F/L=(μo*2*I1*3*I2)/(2*π*r/13) reorganising the terms, we have
F/L=13*6 (μo*I1*I2)/(2*π*r)=78*F/L=(μo*I1*I2)/(2*π*r)=78* F/L initial