Four parallel plates are connected a vacuum as shown in Figure 6. An electron at rest in the hole of plate X is accelerated to the right. The electron passes through holes at W and Y with no acceleration at all. It then passes through the hole at Y and slows down as it heads to plate Z. 6.0 cm-6.0 cm 6.0 cm X W Z G||| 4.0 10 V 7.0 10 V Figure 6 (a) Calculate the speed of the electron at hole W. (b) Calculate the distance, in centimetres, from plate Z to the point at which the electron changes direction.