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

Example Input: Sentence: 'a cat is standing on a green bench looking on'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a woman in high heels walking a dog on a leash'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a cat asleep on a couch next to a dog under a cover'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
4