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 person is kite surfing on calm water while it is cloudy'. How many words start with the letter 'k' in the sentence.
Example Output: 1

Example Input: Sentence: 'a man pitching a baseball from a mound to a home plate'. How many words start with the letter 'a' in the sentence.
Example Output: 4

Example Input: Sentence: 'a street view  left shows a curb  with a yellow fire hydrant and a big bus holding a bicycle in front and to the right an island with cars moving on either side and far off street signs a crosswalk with pedestrians and buildings'. How many words start with the letter 'b' in the sentence.
Example Output:
4