You have a pair of parallel plates (treat them as infinite) seperated by a distance of 1cm. The electric field between them is 1.2x10^5 N/C. You insert a dielectric (with dielectric constant K = 6) of thickness 3 mm between the two plates. What is the change in voltage of a test charge in going from negatively charged plate to the positively charged plate while the dielectric is between the two plates?