DETERMINISTIC MATH MODELS (550.251) HOMEWORK 6 FREQUENTLY ASKED QUESTIONS


1.  PROBLEM 3: When will we be learning regression?

ANSWER: Not for a while.  But you don't need it for this problem.  The
function given IS the result from a regression.

2.  PROBLEM 3: What is a "total sales revenue function"?

ANSWER: total sales revenue = price of item sold * number of items sold.

3.  PROBLEM 5: Demand isn't constant for this problem.  Isn't that a
violation of the EOQ model assumptions?

ANSWER: Sorta.  Part (a) asks you to find the average weekly demand.  It
is an the average that you will use in the remainder of the problem.
(WARNING: make sure all your time units are the same; i.e., all years or
months, or weeks.)  In part (e) you should observe that using an average
(as opposed to a random variable) doesn't impact the EOQ model too much.
This is a nice feature of the EOQ model as stochastic models are MUCH
harder.

4.  PROBLEM 4: How do we find the roots of the derivative?  (It's a
cubic!)

ANSWER: I suggest creating an Excel spreadsheet.  In column one, store
your P values; in column 2 the derivative values.  Assuming I did my work
correctly, I believe the only real root is between 5 and 10.  So evaluate
the derivative for lots of P values between 5 and 10.  Find the P value that
gives a derivative value near zero.