Can you please clarify why the answer is not a1

5. Given the following decision tree for a two-stage (decision) project to enter a joint venture, find the best alternatives (among a, -a, in the figure) and their expected values. The outcomes shown are revenues and the investment expenses are in parentheses. Node 4 represents the situation where alternative a, was chosen, and then the top outcome with a 70 percent probability occurred; note that there is no choice of alternative if the 30 percent probability outcome occurred. Similarly with Node 5. 3,000 0.7 4 a4 1,000 2 (500) 0.3 2,000 0.2 1 500 0.4 0.3 5 1,000 0.5 3,500 , (1,000) 3 a5 3,000 0.6 6 6 4,000