Need help in Present Value and Investment Appraisal problem question

MTG is considering replacing part of its computer network with the latest equipment. The relevant costs of the project and the corresponding savings are given below.

Year = 0

Net cash flow ($) = -100,000

Year = 1

Net cash flow ($) = 20,000

Year = 2

Net cash flow ($)= 30,000

Year = 3

Net cash flow ($) = 40,000

Year = 4

Net cash flow ($) = 50,000

Year = 5

Net cash flow ($) = 20,000

If the current cost of interest in 12% per annum on projects of this type. Calculate the net present value of the project and comment on the course of action to be taken.

Obtain also the NPV for a cost of interest of 20% and thus estimate the Internal Rate of Return.

**I seriously do not know how to do this...Please help me....**