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 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: 'on one plate there is glazed donut and on the other plate there is mug of hot chocolate with a leaf shape swirled in it'. How many words start with the letter 's' in the sentence.
Example Output: 2

Example Input: Sentence: 'a jar of liquid next to a blender full of liquid'. How many words start with the letter 'o' in the sentence.
Example Output:
2