. as of may 31 , 2013 , there was $ 33.5 million of total unrecognized compensation cost related to unvested restricted stock awards that is expected to be recognized over a weighted average period of 2.5 years . employee stock purchase plan we have an employee stock purchase plan under which the sale of 2.4 million shares of our common stock has been authorized . employees may designate up to the lesser of $ 25000 or 20% ( 20 % ) of their annual compensation for the purchase of stock