In this task, you need to count the occurrences of the given word in the given sentence.

Ex Input:
Sentence: 'a person is riding a bicycle but there is a train in the background'. Count the occurrences of the word 'a' in the given sentence.

Ex Output:
3

Ex Input:
Sentence: 'a stuffed animal sitting on a chair in front of a laptop'. Count the occurrences of the word 'a' in the given sentence.

Ex Output:
3

Ex Input:
Sentence: 'a light above a sign that says stop is near a parking garage'. Count the occurrences of the word 'a' in the given sentence.

Ex Output:
3