Answer:
9644
Explanation:
cost of paper on which a card is printed = $0.40 per card
cost of printing = $0.10 per card 
profit made per card sold = $3.75
number of areas where customers are located (n)= 4 
mean of customers from each region = 2300
standard deviation for each region = 200
note : each region is independent 
The optimal production quantity for the card can be calculated going through these steps
first we determine 
the cost of card = $0.10 + $0.40 = $0.50
selling value = $3.75
salvage value = 0 
next we calculate for the z value
= ( selling value - cost of card) /  ( selling price - salvage value )
= ( 3.75 - 0.50 ) / 3.75  = 0.8667
Z( 0.8667 ) = 1.110926 ( using excel formula : NORMSINV ( 0.8667 )
next we calculate 
<em>u</em> = n * mean demand
   = 4 *  2300 = 9200
б =  = 200 * 2
 = 200 * 2 
   = 400
Hence optimal production quantity for the card 
= <em>u</em> + Z (0.8667 ) * б 
= 9200 + 1.110926 * 400
= 9644.3704 
≈ 9644