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

Example 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.
Example Output: 3

Example Input: Sentence: 'a man that is cutting a pizza that is on a stove'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'the tower of a tail building with a flag on the roof and a clock on the upper floor'. Count the occurrences of the word 'the' in the given sentence.
Example Output:
3