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 man using a laptop computer on a table'. How many words start with the letter 'a' in the sentence.
Example Output: 3

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: 'there is a large truck and a yellow truck behind it'. How many words start with the letter 'a' in the sentence.
Example Output:
3