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 picture of a very clean bed in the room'. How many words start with the letter 'r' in the sentence.
Example Output: 1

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: 'a group of people sitting at a long table in  a wine cellar'. How many words start with the letter 'a' in the sentence.
Example Output:
4