Which is true about overnight rates?

	a.	All of the options
	b.	Banks are required to maintain a certain amount of cash, known as a reserve, with the central bank so they borrow at an overnight rate to fulfill the requirement
	c.	The rate at which banks borrow or lend from each other
	d.	Unsecured borrowing and lending between banks as they adjust the reserve requirements, the interest paid is the overnight rate