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 person on a snowboard on a snowy day'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a person leans back while holding onto a flying object'. How many words start with the letter 'a' in the sentence.
Example Output: 2

Example Input: Sentence: 'decorative baseball item hanging from ceiling using baseballs and baseball bats'. How many words start with the letter 'b' in the sentence.
Example Output:
4