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 young man wearing glasses with a tooth brush in his mouth'. How many words start with the letter 'b' in the sentence.
Example Output: 1

Example Input: Sentence: 'this is a living room table with several large chairs placed around it'. How many words start with the letter 'a' in the sentence.
Example Output: 2

Example Input: Sentence: 'a black and white photo of a person with a lot of bags'. How many words start with the letter 'a' in the sentence.
Example Output:
4