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

Example Input: Sentence: 'a man puts his head on his cat sitting on a suitcase'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a sign pointing towards a mcdonalds is posted on a traffic light pole'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a stove that is attached to a blue wall'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
2