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: 'three motorcycle police in front of a crowd attending an outdoor summer event with beer truck behind them'. How many words start with the letter 'p' in the sentence.
Example Output: 1

Example Input: Sentence: 'dusty train passing through a dry mountain valley'. How many words start with the letter 'd' in the sentence.
Example Output: 2

Example Input: Sentence: 'a clean kitchen with an island and stools'. How many words start with the letter 'a' in the sentence.
Example Output:
3