One person won $ 3,000 on their first lottery bet. Fifteen days later he returned to play and won another $ 2,500. Excited about her good luck, she decided to bet $ 100 every 15 days on a constant basis for a certain time. After 21 consecutive fortnightly bets without getting any prize, he decided not to bet anymore. Determine the rate of return this person earned by entering the gaming world let the calculation be at hand, excel no.