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

Example Input: Sentence: 'a group of people in a field flying kites'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a group of kites flying in a blue cloudy sky'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 2

Example Input: Sentence: 'a dog is sitting in a field of grass waiting for someone to occupy an empty chair'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
2