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

Example Input: Sentence: 'a delivery truck for a library parked by a meter'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a train on a train track next to a concrete platform'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a man walking through a forest while wearing a hat'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3