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: '{3, 4, 5, 7, 9, 12}', Set2: '{11, 3}'. How many elements are there in the intersection of Set1 and Set2 ?
[A]: 1


[Q]: Set1: '{18, 20, 7}', Set2: '{17, 9}'. How many elements are there in the intersection of Set1 and Set2 ?
[A]: 0


[Q]: Set1: '{1, 3, 6, 8, 11, 15}', Set2: '{1, 7, 9, 10, 12, 13, 15, 19, 20}'. How many elements are there in the intersection of Set1 and Set2 ?
[A]:
2