3. (Newsvendor Model) The Katie's Card Shop sells calendars with different Colonial pictures shown for each month. The once-a-year order for each year's calendar arrives in September. From past experience the September to March demand for the calendars can be approximated by a normal distribution with mean 500 and standard deviation 120 . The calendars cost $1.50 each, and Katie sells them for $3 each. (a) If Katie throws out all unsold calendars at the end of March (i.e., salvage value is zero), how many calendars should be ordered? (b) If Katie reduces the calendar price to $1 at the end of March and can sell all surplus calendars at this price, how many calendars should be ordered