Let the following relation schemas be given:

R = (A, B, C)

S = (D, E, F)

Let relations r(R) and s(S) be given. Give an expression in the tuple relational calculus that is equivalent to each of the following:

A. II_A(r)

B. _{B = 19} (r)

C. r s

D. II_{A, F} (_{C = D} (r s))

NOTE:PLEASE Writing is not recommended by hand