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

Example Input: Sentence: 'a cat that is laying down on a bed'. Count the occurrences of the word 'is' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a child laying on a bed with his head hanging up side down and a teddy bear leaning against the bed'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a large bird sitting on a tree branch'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
2