Is it possible to compute the answer using the node 2 (a,c),node 5(a,c,b) node 6(a,c d), node 7 (a,c,e), node 8(a,c,b,d), node 9 (a,c,d,e), node 10(a,c,d,b),node 11(a,c,d e)? Is that answer viable? Note that in this case, we are violating the condition that 'c' should not be before 'b'