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: 'people on a tour bus with half the top cut off'. How many words start with the letter 'b' in the sentence.
Example Output: 1

Example Input: Sentence: 'a group of people sitting at a restaurant table'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a woman in light blue dress playing a game of tennis'. How many words start with the letter 'o' in the sentence.
Example Output:
1