Each month a store owner can spend at most $500 on carrots and cucumbers. A carrot costs the store owner $0.30 and a cucumber costs the store owner $0.50. Each carrot is sold for a profit of $0.75 and each cucumber is sold for a profit of $0.80. The owner estimates that the number of cucumbers sold is at most a third of the number of carrots sold. He also estimates that at least 300 carrots but at most 500 carrots are sold each month. How many of each, carrots and cucumbers, should be sold in order to maximize the profit?