For each of the following Datalog rules, write an expression of relational algebra that defines the same
relation as the head of the rule:
i. P(x, y)  Q(x, z) AND R(z, y)
ii. P(x, y)  Q(x, z) AND Q(z, y)
iii. P(x, y)  Q(x, z) AND R(z, y) AND x < y