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 small airplane sitting on top of a runway'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a man wearing a beret while using a laptop computer'. How many words start with the letter 'u' in the sentence.
Example Output: 1

Example Input: Sentence: 'many people are flying kites on a beach'. How many words start with the letter 'a' in the sentence.
Example Output:
2