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

Example Input: Sentence: 'a horse and a dog facing each other in a brown field of grass'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a woman cutting cake while another woman is holding a plate'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a little boy riding a skateboard inside of a small room'. Count the occurrences of the word 'boy' in the given sentence.
Example Output:
1