Join size estimate and primary key. (10 points) Consider three relations rl, r2 and r3, with schemas R1(ABC), R2CDE) and R3(EF), respectively (underlined attributes indicate primary keys). Assume that rl has 1000 tuples, r2 has 600 tuples, and r3 has 1,200 tuples. (i Estimate the size of natural join of three relations rl x r2 x r3. Explain how to get your answer ii Now suppose in R1, C (instead of A) is the primary key (i.e., we have RI(ABC)). Estimate the size of natural join of three relations rl x r2 x r3 Explain how to get your