5. Give an exact answer for each part, and explain the reason for your answer (a.) (4 points) How many four-digit positive integers are there in which all the digits are different? (b.) (4 points) How many bitstrings of length ten are made up of five zeros and five ones? (c.) (4 points) How many strings of length ten consist of two different digits alternating? For example, 4747474747 (d.) (4 points) For about $25, you can build your own lightsaber at Disneyland and fulfill you dream of becoming a Jedi Master or a Sith Lord. A lightsaber mstilude an emitter, a blade, and a hilt. Suppose you get to choose from 5 types of emitters, 4 types of blade colors, and 2 types of hilts. In addition, you also have the option of adding a switch, an accessory ring, a customized hilt sleeve, an adapter. How many way are there to build your lightsaber in total