Q#1:

Q#2:

We are given the following table:

        Activity        d
        (1,2)           6
        (1,3)           4
        (2,4)           3
        (3,4)           9
        (3,5)           10
        (3,6)           12
        (4,7)           9
        (5,7)           2
        (6,8)           3
        (7,9)           15
        (8,9)           9

The earliest start time (ET) & latest start time (LT) are:

        Node    ET      LT
        1       0       0
        2       6       10
        3       4       4
        4       13      13
        5       14      20
        6       16      25
        7       22      22
        8       19      28
        9       37      37

For each activity (i,j),
        total float is  TF(i,j) = LT(j) - ET(i) - t_ij,
        free float is   FF(i,j) = ET(j) - ET(i) - t_ij.

        Activity        TF      FF
        (1,2)           4       0
        (1,3)           0       0
        (2,4)           4       4
        (3,4)           0       0
        (3,5)           6       0
        (3,6)           9       0
        (4,7)           0       0
        (5,7)           6       6
        (6,8)           9       0
        (7,9)           0       0
        (8,9)           6       9

So, the critical path is 1-3-4-7-9.