Anyone help please

Thompson Mining operates a silver mine in Nevada. Acquisition, exploration and development costs totaled $4.2 million. After the silver is extracted, Thompson has the obligation to restore the land and create a wildlife preserve. This is expected to be in 5 years. The company has the following three estimates for restoration costs: $500,000 (30% probability), $750,000 (40% probability), and $1,000,000 (30% probability). The companys credit-adjusted, risk-free rate of interest is 5%. Please show the computation of the initial cost of the silver mine.