With regard to the reinvestment rate assumption:

		NPV assumes reinvestment at the risk free rate, while IRR assumes reinvestment at the cost of capital
		IRR assumes reinvestment at the internal rate of return, while NPV assumes reinvestment at the cost of capital.
		Both NPV and IRR assumes reinvestment at the cost of capital.
		NPV assumes reinvestment at the cost of capital, while IRR assumes reinvestment at the risk free rate
		NPV assumes reinvestment at the internal rate of return, while IRR assumes reinvestment at the cost of capital.