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

Example Input: Sentence: 'a red and a white train cab on a rusty train track'. Count the occurrences of the word 'rusty' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a group of three toilets with a person standing in front of the middle one'. Count the occurrences of the word 'toilets' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a big clock on top of a building in a city'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3