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: 'some very pretty giraffes standing by a big fence'. How many words start with the letter 'f' in the sentence.
Example Output: 1

Example Input: Sentence: 'a woman that is holding up a banana'. How many words start with the letter 'w' in the sentence.
Example Output: 1

Example Input: Sentence: 'some big and little sheep standing around in some green grass'. How many words start with the letter 'a' in the sentence.
Example Output:
2