7.31 Consider the schema R=(A,B,C,D,E,G) and the set of functional dependencies: ABCD BD DE B DEG AB AC DE R is not in BCNF for many reasons, one of which arises from the functional dependency ABCD. Explain why AB + CD shows that Ris not in BCNF and then use the BCNF decomposition algorithm starting with AB + CD to generate a BCNF decomposition of R. Once that is done, determine whether your result is or is not dependency preserving, and explain your reasoning