A fitness center offers one-to-one private lesson everyday and needs to decide the number of coaches in advance. The center pays $140 for a coach scheduled to work on a specific day, regardless of whether the coach actually teaches a lesson or not. The unit cost for processing a customer's request is $6, no matter the customer is assigned a coach or not. The center charges customers $250 for a lesson taught. If a customer cannot get a coach, the loss of customer's goodwill is $18. The center estimated that the daily demand for the lesson is normally distributed with a mean of 90 coaches and a standard deviation of 14 coaches.

Given the above information, answer the following questions:
1. What inventory model should be used to determine the number of coaches to schedule to maximize the total expected daily profit for the center? Why?
2.  What is the salvage value, purchase price and cost? How many coaches should be scheduled each day to maximize the total expected profit? Provide your answer in integer.