BCNF Decomposition no key for relation

Question

i am trying to understand how to normalize a relation to BCNF. The task at hand, involves a relation and a set of functionel dependencies.

They look somewhat in the lines of;

R(A,B,C,D,E)

F {
AB->C
C->D
}

Now i am trying to calculate the keys for R, by calculating the Closure. Problem is, the E attribute is not mentioned in the FD's. So how do i find out what is the Key for the relation?

Answer 1

Add the trivial dependency ABCDE->ABCDE to F. Then determine the key.