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 yellow fire hydrant is placed in the grass'. How many words start with the letter 'i' in the sentence.
Example Output: 2

Example Input: Sentence: 'a young boy hits a baseball during a game'. How many words start with the letter 'd' in the sentence.
Example Output: 1

Example Input: Sentence: 'an old photo of a person and a horse'. How many words start with the letter 'a' in the sentence.
Example Output:
4