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, 4, 5, 9, 10, 15, 17, 20}', Set2: '{4, 6, 10, 11, 15, 17, 18, 20}'. How many elements are there in the union of Set1 and Set2 ?
[A]: 11


[Q]: Set1: '{1, 3, 5, 6, 7, 13, 16}', Set2: '{18, 7}'. How many elements are there in the union of Set1 and Set2 ?
[A]: 8


[Q]: Set1: '{9, 4, 15}', Set2: '{1}'. How many elements are there in the union of Set1 and Set2 ?
[A]:
4