1. Compute the closure for relation schema R(A,B,C,D,E), given the set of FD 's: F={ABC, CDE,BD,EA}, and List the candidate keys for R. 2. For each of the following transformations expressed in relational algebra, give an intuitive explanation of what it means and determine its validity. a. L1=L1(R) b. (RS)T=R(ST) c. c/Bc0(R)C=c0Bc/(R)C