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

Example Input: Sentence: 'a little kid skiing down a hill holding ski poles'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a pizza sitting on top of a pan on top of a table'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a pink toothbrush and a blue toothbrush sitting in a clear glass toothbrush holder by a mirror'. Count the occurrences of the word 'toothbrush' in the given sentence.
Example Output:
3