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

Example Input: Sentence: 'a freckled white horse standing in a grassy area'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a pizza is on a cooling rack on a counter'. Count the occurrences of the word 'on' in the given sentence.
Example Output: 2

Example Input: Sentence: 'there are some chairs under an umbrella at the beach'. Count the occurrences of the word 'at' in the given sentence.
Example Output:
1