First problem:''From a company of 12 soldiers, a squad of 4 is chosen each night.

a) For how many nights a squad go on duty without tow of the squads being identical ?

b) In how many of these squads would a particular soldier be included ?''

For a), x=4, n= 12 using Combinatory analysis and found 495

For b) I multiplied C x=4 n=12 by C x=1 n=4 and got 1980

Anyone can confirm my results?

2nd problem:

I'm stuck in this following problem:

'' A publishing company sells 400,000 copies of a certain book each year. Ordering the entire amount printed at the beginning of the year ties up valuable storage space and capital. However, running off the copies in several partial runs throughout the year results in added costs for setting up each printing run. Setting up each production run costs $1,000. The carrying costs, figured on the average number of books in the storage, are 50 cents per book. Find the economic lot size, that is, the production run size that minimizes the total setting up and carrying costs. ''

My guess was to say that the cost function is: C(x) = 1000 + 0.50(x)

I'm having a hard time even understanding what the problem is all about.

HELP?