statistics
posted by iyra .
Blossom's Flowers purchases roses for sale for Valentine's Day. The roses are purchased for $10 a dozen and are sold for $20 a dozen. Any roses not sold on Valentine's Day can be sold for $5 per dozen. The owner will purchase 1 of 3 amounts of roses for Valentine's Day: 100, 200, or 400 dozen roses. The payoff for buying and selling 400 dozen roses at the full price is:
$12,000
$6,000
$4,000
It cannot be determined.

The cost of the roses is $4000. Subtract that from cost of the dozens that are sold at $20 (full price).
You are given much extraneous information (information that is not needed) in the third and fourth sentences.
$8000  $4000 = ?
You need to read the problem carefully.
I hope this helps. 
$4000