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 vine of bananas sit on a tree'. How many words start with the letter 'b' in the sentence.
Example Output: 1

Example Input: Sentence: 'a fire truck and an ambulance driving down the street'. How many words start with the letter 'a' in the sentence.
Example Output: 4

Example Input: Sentence: 'four cows stand in a field near a barbed wire fence'. How many words start with the letter 'f' in the sentence.
Example Output:
3