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 green place mat sitting on a table with a couple of plates of food and a drink placed upon it'. How many words start with the letter 'p' in the sentence.
Example Output: 3

Example Input: Sentence: 'a brown dog sitting next to a brown cat on a bed'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a couple of horses in a field at a ranch'. How many words start with the letter 'a' in the sentence.
Example Output:
4