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

Example Input: Sentence: 'a person taking a photo of a person brushing her teeth'. Count the occurrences of the word 'of' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a woman sleeps in a bed with a pillow and sheet'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a man riding a water ski while being towed by a boat'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3