Payoff matrix

You have been approached about investing $100,000 in a gas and oil well venture. You are told that the probability of striking oil is 20% and if you do that the value of your share will be $500,000. The probability of gas is 40% and the value of that is $200,000. The probability of a dry hole is 40% and it will cost you $50,000 to clean up the environmental damage for a dry hole. Calculate expected value and expected rate of return on your investment