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 large body of water with a boat on it'. How many words start with the letter 'o' in the sentence.
Example Output: 2

Example Input: Sentence: 'a refrigerator a white cabinet a microwave and some blue walls'. How many words start with the letter 'b' in the sentence.
Example Output: 1

Example Input: Sentence: 'a group of people that are by and elephant'. How many words start with the letter 'a' in the sentence.
Example Output:
3