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 baseball player holding a glove in one hand and ball in the other'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a person is speaking in a public room'. How many words start with the letter 'i' in the sentence.
Example Output:
2