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 bus is parked on the side of a road in front of a building'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'an old fashion picture of a man dressed formally'. How many words start with the letter 'd' in the sentence.
Example Output:
1