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 black and white photo of a young man riding a horse'. How many words start with the letter 'a' in the sentence.
Example Output: 4

Example Input: Sentence: 'a photo of a waterway with several boats along the shore'. How many words start with the letter 'w' in the sentence.
Example Output: 2

Example Input: Sentence: 'a speaker at a podium talking to air national guard'. How many words start with the letter 'a' in the sentence.
Example Output:
4