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

Example Input: Sentence: 'an employee at a canon store stands in front of a case of canon merchandise'. Count the occurrences of the word 'of' 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 television that is on top of a dresser in a living room'. Count the occurrences of the word 'on' in the given sentence.
Example Output:
1