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

Example Input: Sentence: 'a woman is riding a wave on a surfboard'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a white plate sitting next to a cup of liquid on top of a table'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a man riding a brown horse next to a group of white horses'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3