A merchandise vendor at a sports arena is given a large uncounted pile of hats and shirts to sell at a game. Hats cost $15.00 each, and shirts sell for $21.00 each. At the end of the night, the vendor realized he forgot to keep track of how many quantities of each item he sold. However, he does know that he sold 64 total items and sold $1,164.00 of merchandise. How many hats did he sell