In this task, you are given two sets, and you need to count the number of elements at the intersection of two given sets.  A Set is shown by two curly braces and comma-separated numbers inside, like {1, 2, 3}. The intersection of two given sets is the largest set which contains all the elements that are common to both sets. To find the intersection of two given sets, A and B is a set consisting of all the elements common to both A and B.

Q: Set1: '{2, 3, 6, 7, 9, 10, 11, 17, 20}', Set2: '{1, 7, 10, 16, 17}'. How many elements are there in the intersection of Set1 and Set2 ?

A: 3
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Q: Set1: '{2, 4, 5, 8, 9, 10, 12, 13, 17}', Set2: '{1, 3, 7, 8, 10, 15, 18}'. How many elements are there in the intersection of Set1 and Set2 ?

A: 2
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Q: Set1: '{17, 19, 4, 1}', Set2: '{2, 4, 5, 6, 16, 17, 19}'. How many elements are there in the intersection of Set1 and Set2 ?

A:
3
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