Christina, a materials engineer, has discovered a groundbreaking new way to make recycled plastic stronger. She is looking to exploit this discovery by starting up his own business at a cost of $500 000. Unfortunately Christina has only $200 000 in savings and must borrow the other $300 000. If the interest rate is 10%, then what, according to an economist, is the opportunity cost of starting up the business?
(Hi, this is my question, I know the answer, but I do not know why, so please explain clearly, thank you so much)