Along, straight wire carries a current of 12.5 a. an electron travels at 61300 m/s parallel to the wire, 57.4 cm from the wire. the permeability of free space is 1.25664 x 10-6 n/a² and the charge on an electron is 1.6 x 107 what force does the magnetic field of the current exert on the moving electron?

i think its c if i'm wrong

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.