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: 'people walking down the street while some people ride their bicycles'. How many words start with the letter 'w' in the sentence.
Example Output: 2

Example Input: Sentence: 'a stop sign and a no stopping sign are on a street corner'. How many words start with the letter 's' in the sentence.
Example Output: 5

Example Input: Sentence: 'a man scratches the head of a relaxing house cat'. How many words start with the letter 'c' in the sentence.
Example Output:
1