AVAILABLE resources 1 5 2 2 ( assume always in order U,V,W,X )
with the available resources you can complete A,C,D....
1) Complete A first then available resources are 1 5 3 4 .... you can't complete E or B ... but either of C or D completion you can complete E or B...
A C ( B,D,E are in any order ) ------ 3! =6
A D ( B,C,E are in any order ) ------ 3! =6
2) Complete C first then available resources are 2 8 7 6 .... you can complete E or B or A or D in any order
C ( A,B,D,E are in any order ) ------ 4! =24
3) Complete D first then available resources are 1 11 5 4 .... you can complete E or B or A or C in any order
D ( A,B,C,E are in any order ) ------ 4! =24
Total Safe sequences = starts with A + starts with C + starts with D = 12+24+24 = 60
