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 street sign above a faded stop sign'. How many words start with the letter 's' in the sentence.
Example Output: 4

Example Input: Sentence: 'a person on a snowboard on a snowy day'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a train is pulling up to a platform near a building'. How many words start with the letter 'n' in the sentence.
Example Output:
1