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.

Set1: '{6, 7, 9, 12, 13, 15, 16, 17, 18}', Set2: '{1, 5, 8, 12, 16, 17}'. How many elements are there in the intersection of Set1 and Set2 ?
3

Set1: '{1, 8, 9, 13, 17, 18, 19, 20}', Set2: '{1, 3, 5, 10, 12, 13, 15, 17, 18}'. How many elements are there in the intersection of Set1 and Set2 ?
4

Set1: '{10, 19, 13, 7}', Set2: '{1, 4, 5, 6, 13, 15, 16, 18}'. How many elements are there in the intersection of Set1 and Set2 ?

1