Here are declarations of two relations R and S: CREATE TABLE S( C INT PRIMARY KEY d INT CREATE TABLE R( a INT PRIMARY KEY b INT REFERENCES S(c) R(a,b) currently contains the four tuples (0,4), (1,5), (2,4), and (3,5). S(c,d) currently contains the four tuples (2,10), (3,11), (4,12), and (5,13). As a result, certain insertions and deletions on R and S are illegal. You should develop simple tests for illegal operations of these four kinds. Then, show your understanding by indicating which of the following modifications will not violate any constraint. a) Deleting (1,5) from R b) Deleting (4,12) from S c) Inserting (3,4) into R d) Inserting (4,10) into S