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

Example Input: Sentence: 'three elephants standing between a fence and a road'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a vehicle applying brakes near a stop sign on a rainy day'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a cat sitting next to a window looking out on a bird'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3