8.David invests 100 dollars in a stock. Each year his investment doubles in value with probability 0.4 and decreases in value by 50% with probability 0.6. What is the expected value of David's investment after 20 years?
(A) 90
(B) 110
(C) 259
(D) 673
(E) 1745

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統計： A(0), B(1), C(0), D(1), E(0) #2852334