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 boy in a red baseball uniform throws a ball'. How many words start with the letter 'b' in the sentence.
Example Output: 3

Example Input: Sentence: 'woman standing on the beach with a large sailboat behind her'. How many words start with the letter 's' in the sentence.
Example Output: 2

Example Input: Sentence: 'man standing in a living room in front of a cupboard'. How many words start with the letter 'a' in the sentence.
Example Output:
2