2. R and R2 are two relations whose current instances contain N and N2 tuples re- spectively, where N2 > N1 > 0. What are the maximum and minimum possible sizes (in number of tuples) for the relation produced by each of the following relational algebra expressions? For each, state any assumption you need to make about the schemas of R1 and R2 in order to make the expression meaningful. $1. RU R2 $2. R1 R2 $3. R1 x R2 $4. Oa>2(R1) $5. R1 + R2