In this task, you are given two sets, and you need to count the number of elements at the union of two given sets. A Set is shown by two curly braces and comma-separated numbers inside, like {1, 2, 3}. Union of two given sets is the smallest set which contains all the elements of both the sets. To find the union of two given sets, A and B is a set that consists of all the elements of A and all the elements of B such that no element is repeated.

Q: Set1: '{2, 3, 4, 5, 7, 15, 20}', Set2: '{4, 5, 8, 9, 10, 11, 14, 17, 20}'. How many elements are there in the union of Set1 and Set2 ?

A: 13
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Q: Set1: '{17, 18, 4}', Set2: '{3, 7, 8, 11, 15, 16, 17, 19}'. How many elements are there in the union of Set1 and Set2 ?

A: 10
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Q: Set1: '{15}', Set2: '{2, 5, 6, 9, 10, 12, 13, 16, 20}'. How many elements are there in the union of Set1 and Set2 ?

A:
10
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