Exercise 19.10 suppose you are given a relation r(a, b, c, d). for each of the following sets of fds, assuming they are the only dependencies that hold for r, do the following: (a) identify the candidate key(s) for r. (b) state whether or not the proposed decomposition of r into smaller relations is a good decomposition and briefly explain why or why not. 1. b --+ c, d --+ a; decornpose into bc and ad. 2. ab -+ c, c -~~ a, c d; decompose into a cd and be. ~~. a bc, c -+ ad; decornpose into abc and ad. 4. a b, b c, c '-1 d; decornpose into ab and a cd. 5. a --+ b, b -+ c, c d; decoinpose into ab, ad and cd.