(14: a) Consider the design of a communication system. i. Howr many threedigit phone prefixes that are used to represent a particular geographic area [such as an area code) can be created from the digits [l through 9? ii. As in part 1., how many threedigit phone prefixes are possible that do not startwith i} or 1, but contain U or 1 as the middle digit? iii. Howr many threedigit phone prefixes are possible in which no digit appears more than once in each prefix? b] Suppose that an operating room needs to handle three knee, four hip, and five shoulder surgeries. i. Howr many different sequences are possible? ii. How many different sequences have all hip, knee, and shoulder surgeries scheduled consecutively? iii. Howr many different schedules begin and end with a knee surgery