Blossom's Flowers Purchases Roses for Sale for Valentine's Day

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.
-If the probability of selling 100 dozen roses is 0.2 and 200 dozen roses is 0.5,then the probability of selling 400 dozen roses is _______.

A) 0.7
B) 0.5
C) 0.2
D) 0.3