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

Example Input: Sentence: 'a man is looking slyly at the camera while sitting at his laptop at a desk'. Count the occurrences of the word 'at' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a black bird sitting on a wall next to grass'. Count the occurrences of the word 'next' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a woman with a tennis racquet trying to hit a ball'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3