What is the total electromagnetic force on a particle with c

What is the total electromagnetic force on a particle with charge q = 10 nC moving with a speed v = 3/5c in the +x direction in a region where the electric and magnetic fields are vector E = [0, 0, 3000 N/C] and vector B = [0, 5000 N/C, 0]

Solution

Electric force = qE = 3 * 10^-5 k^{^} N
Magnetic force = qV X B = 10*10^-9*.6*3*10^8*5000 i^{^} X j^{^} N = 9000 N

So total force is dominated by Magnetic field at 9000 N