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 little white airplane that is parked on some concrete'. How many words start with the letter 'p' in the sentence.
Example Output: 1

Example Input: Sentence: 'a stop sign and a no stopping sign are on a street corner'. How many words start with the letter 's' in the sentence.
Example Output: 5

Example Input: Sentence: 'two park benches sitting in grass under dappled sunlight'. How many words start with the letter 's' in the sentence.
Example Output:
2