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 group gathering in which several people are holding frisbees'. How many words start with the letter 'g' in the sentence.
Example Output: 2

Example Input: Sentence: 'a clock tower is standing next to palm trees'. How many words start with the letter 't' in the sentence.
Example Output: 3

Example Input: Sentence: 'a black cat is sitting on a wood bench'. How many words start with the letter 'b' in the sentence.
Example Output:
2