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 person is standing by a pier near a fire hydrant'. How many words start with the letter 'p' in the sentence.
Example Output: 2

Example Input: Sentence: 'a man wearing a beret while using a laptop computer'. How many words start with the letter 'u' in the sentence.
Example Output: 1

Example Input: Sentence: 'a group of students are skiing together on the slope'. How many words start with the letter 's' in the sentence.
Example Output:
3