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 in a black tennis outfit playing tennis on a red clay court'. How many words start with the letter 'r' in the sentence.
Example Output: 1

Example Input: Sentence: 'two men on ski boards in the midst of a blizzard'. How many words start with the letter 's' in the sentence.
Example Output: 1

Example Input: Sentence: 'a man laying down in a hospital bed next to bottles of medicine'. How many words start with the letter 'b' in the sentence.
Example Output:
2