Leo invested a certain amount of money for one year. he invested $1,000 of the amount at c percent simple annual interest and the rest of the amount at d percent simple annual interest. if the amount that leo invested at c percent annual interest and the amount that he invested at d percent annual interest earned $30 in interest for that year, what was the total amount that leo invested for that year?
(1) c - d = 1
(2) c = 0.75d