What is the payback period and discounted payback period ?

Seth Bullock, the owner of Bullock Gold Mining, is evaluating a new gold mine in South Dakota. Dan Dority, the company's geologist, has just finished his analysis of the mine site. He has estimated that the mine would be productive for eight years, after which the gold would be completely mined. Dan has taken an estimate of the gold deposits to Alma Garrett, the company's financial officer. Alma has been asked by Seth to perform an analysis of the new mine and present her recommendation on whether the company should open the new mine.

Alma used the estimates provided by Dan to determine the projected after-tax, incremental cash flow inflows that would be generated during the life of this project (see below). The cost to open this mine is estimated to be $600,000,000 and it is expected that closing the mine at the end of its useful life (and reclaim the surrounding area) will result in an additional cost that is already reflected in the net cash flow for Year 8 presented below.

Bullock Mining has a 12% required rate of return on its mining project, and a maximum acceptable payback period of 4 years.

Year	Cash
1	$50,000.00
2	$80,000,000
3	$150,000,000
4	$210,000,000
5	$210,000,000
6	$105,000,000
7	$125,000,000
8	$25,000,000

What is the payback period and Discounted Payback period?