In this task, you need to count the number of words in a sentence that start with the given letter. Answer with numbers and not words.

Example Input: Sentence: 'a woman is holding the hand of a boy who is leaning on a fire hydrant'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a man on a cell phone next to a woman'. How many words start with the letter 'n' in the sentence.
Example Output: 1

Example Input: Sentence: 'a white van is travelling beside a giraffe'. How many words start with the letter 't' in the sentence.
Example Output:
1