TASK DEFINITION: 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.
PROBLEM: Set1: '{8, 9, 10, 11, 12, 13, 16, 19, 20}', Set2: '{3, 4, 7, 8, 9, 12, 14, 15, 18, 19}'. How many elements are there in the intersection of Set1 and Set2 ?

SOLUTION: 4

PROBLEM: Set1: '{1, 8, 9, 10, 11, 13, 17, 18, 19, 20}', Set2: '{1, 5, 10, 12, 13, 15, 16, 20}'. How many elements are there in the intersection of Set1 and Set2 ?

SOLUTION: 4

PROBLEM: Set1: '{3, 5, 8, 10, 12, 14, 15, 17}', Set2: '{3, 8, 9, 15, 17}'. How many elements are there in the intersection of Set1 and Set2 ?

SOLUTION:
4