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: 'some signs and the roof of a train station'. How many words start with the letter 'a' in the sentence.
Example Output: 2

Example Input: Sentence: 'a boy waves at the camera standing on a tree stump'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a baby is sitting on a toilet with a toothbrush in its mouth'. How many words start with the letter 't' in the sentence.
Example Output:
2