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 sitting on a stone wall using a cellular phone'. How many words start with the letter 's' in the sentence.
Example Output: 2

Example Input: Sentence: 'a bedroom area with bed two dressers and a window'. How many words start with the letter 'w' in the sentence.
Example Output: 2

Example Input: Sentence: 'a living room with hd tv chair and decorations'. How many words start with the letter 'r' in the sentence.
Example Output:
1