Make some assessments of the maintenance scheduling of a ship. Use PERT three-estimate approach. You are to identify slack and critical activities in the schedule using the PERT mean time. Further, you are to determine the date and time to enter the dry-dock so that with a 80 % probability, the vessel can be finished with the maintenance by the 15th of April 2022 at 12:00 UTC. Make necessary assumptions. You should make use of Excel to do the estimates.

Below are the activities that are mapped out for the maintenance to be done on the ship.

Activity	Immediate predecessor	Optimistic estimate	Most likely estimate	Pessimistic estimate
A	-----	1	1	3
B	A	1	2	3
C	B	3	4	6
D	B	1	2	3
E	B	2	3,5	8
F	C	1	1	1
G	C	1	1	2
H	C	3	3	4
I	F	1	2	3
J	F	1	3	6
K	G	1	3	4
L	G	3	5	7
M	G	1	2	3
N	H	3	4	6
O	DE	2	4	5
P	D	3	5	6
Q	I	2	3	5
R	IJK	3	3	4
S	L	2	3	4
T	L	3	3	6
U	N	2	5	9
V	N	2	4	7
W	OP	3	5	8
X	Q	4	5	7
Y	RST	1	2	3
Z	MUV	3	4	6
*a	W	2	2	3
*b	W	1	3	4
*c	OXYZ	1	2	3
*d	*a *b	2	3	5
*e	*c	2	3	4

The activities noted *a, *b are not special activities, and are to be considered as the other activities.