Toll road investments are usually realized through Build-Operate-Transfer (BOT) projects. Since these projects last for a long period of time, they are exposed to various risks. The successful delivery of BOT projects implies that these risks are efficiently mitigated. In order to alleviate project risks, the public partner may offer the private partner the possibility of abandoning the project and transferring it back to the public sector for a specific pre-determined price. In one such project, the public partner offers the private partner the possibility of abandoning the project within 4 years for the salvage value of $80 million. 

Use one of the binomial option pricing technique to value this option? 

Assume that the present value of future cash flows from the toll road investment is $100 million and it can go up or down once a year. The volatility is 30% per annum. The risk-free rate is 5%.