Mary borrowed $21,500 to buy a truck for her business. She borrowed from her parents who charge her 3% simple interest. She borrowed from a credit union that charges 5% simple interest, and she borrowed from a bank that charges 6% simple interest. She borrowed four times as much from her parents as from the bank, and the amount of interest she paid at the end of 1 yr was $865 . How much did she borrow from each source?