In this task, you need to count the occurrences of the given word in the given sentence.
Example: Sentence: 'the brown cat sits perched on atop of the bed peering forward'. Count the occurrences of the word 'the' in the given sentence.
Example solution: 2
Example explanation: The word 'the' appears two times in the given sentences. So, the answer is 2.

Problem: Sentence: 'a bench sitting under a mirror and next to a wall'. Count the occurrences of the word 'a' in the given sentence.

Solution: 3