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

Example Input: Sentence: 'a small bird perched on a branch in a tree'. Count the occurrences of the word 'a' in the given sentence.
Example Output: 3

Example Input: Sentence: 'a man wearing jeans and a tshirt with a cell phone on his belt'. Count the occurrences of the word 'belt' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a surfer splashes water up from a wave'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
2