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 msall bus going down a road with a street sign'. How many words start with the letter 'd' in the sentence.
Example Output: 1

Example Input: Sentence: 'a green place mat sitting on a table with a couple of plates of food and a drink placed upon it'. How many words start with the letter 'p' in the sentence.
Example Output: 3

Example Input: Sentence: 'a skier takes a turn down a slope of snow'. How many words start with the letter 'a' in the sentence.
Example Output:
3