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 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: 'an illustration of a kitchen is shown in vintage'. How many words start with the letter 'i' in the sentence.
Example Output:
3