The daily demand for substitute teachers in the Metro Manila public school system follows the probability distribution given in the table below. The agency head wants to know how many teachers they must keep in the substitute teacher pool. Whether or not the substitute teacher is needed, it costs PhP900 per day to keep a teacher in the pool. However, if not enough substitute teachers are available on a given day, regular teachers are used to covering the classes at a cost of PhP1650 per regular teacher.

Number Needed	Probability
200	0.03
275	0.03
350	0.03
400	0.05
450	0.4
500	0.3
550	0.06
600	0.07
650	0.03

1	What is the critical ratio?
2	How many substitute teachers should be kept in the pool?
3	What is the total expected cost?

Answer rating: 100% (QA)

1 The cost to keep the substitute teacher PHP 900 day The cost to ... View the full answer