EXCEPT operator

Question

R and S are compatible relation .R=9 tuples S=6 tuples.Find minimun and maximum number of tuples in the result R-S.

Comments

Answer is 3, 9

but if we consider tuples like  R(AB)={(1,1)  (2,2)  (2,2)}   S(CD)={(1,1)  (2,2)}

then minimum should be 0.   so answer  should be 0,9 .   am i right ?

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no man ,

a relation can't have redundant tuple

Answer 1

 minimum is 3

maximum is 9

How??