Mariah has decided to hire three workers. To determine whom she will hire, she has selected a group of 20 candidates. She plans to have one working interview with 3 of the 20 candidates every day to see how well they work together. How many days will it take her to have working interviews with all the different combinations of job candidates?
Choose the correct choice from the following answers:	A) 520	B) 120	C) 300	D) 30	E) 333

Rationale: 520 . answer a
Answer: A