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

Input: Consider Input: Sentence: 'a young boy at a picnic table is holding half a donut'. Count the occurrences of the word 'a' in the given sentence.

Output: 3

Input: Consider Input: Sentence: 'a guy hitting a ball at a professional baseball game'. Count the occurrences of the word 'a' in the given sentence.

Output: 3

Input: Consider Input: Sentence: 'a surfer riding a wave back to the shore'. Count the occurrences of the word 'a' in the given sentence.
Output: 2