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

Example Input: Sentence: 'a black and white photo of an airplane being loaded'. Count the occurrences of the word 'of' in the given sentence.
Example Output: 1

Example Input: Sentence: 'a large building with a cross at the very top and a clock below it'. Count the occurrences of the word 'cross' in the given sentence.
Example Output: 1

Example Input: Sentence: 'scenic picture of a city and a harbor on a cloudy day with green trees'. Count the occurrences of the word 'a' in the given sentence.
Example Output:
3