Across two periods, there are four possibilities: an up move followed by an up move ($121.00 end value), an up move followed by a down move ($101.20 end value), a down move followed by an up move ($101.20 end value), and a down move followed by a down move ($84.64 end value). The probability of an up move followed by a down move is 0.40 times 0.60 equals 0.24. The probability of a down move followed by an up move is 0.60 times 0.40 also equals 0.24. Both of these sequences result in an end value of $101.20. Therefore, the probability of an end value of $101.20 is 48%.