This is all the info there is.... to answer the questions...what do you mean "durations" ? A set of activities and their times (in days) are provided for a project along with their dependencies. The times are a=optimistic, b=pessimistic, and m=most likely.
ACTIVITY	a	m	b	Immediate Predecessor(s)
A	4.2	8.4	11.2	-
B	2.8	5.6	5.6	-
C	1.4	2.8	4.2	-
D	8.4	9.8	11.2	C
E	2.8	5.6	8.4	B,D
F	8.4	14	19.6	A,E
G	1.4	2.8	5.6	A,E
H	4.2	8.4	12.6	F
I	14	15.4	16.8	G
J	19.6	22.4	28	C
K	2.8	11.2	14	H,I
Calculate the Expected Times of Completion for each activity.
What is the Expected Time of Completion and the standard deviation of the project (based on AON diagram using critical path (CPM))?
Calculate Slack1 and Slack 2 for all activities of the project.
What is the probability of completing the project in 55 days?
Prepare a complete Gannt Chart for the project showing activities (based on time of completion for each and dependencies) and slack.