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 close up of a traffic light on a city street'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'hospital display of different bed setups and a nurses uniform'. How many words start with the letter 'd' in the sentence.
Example Output: 2

Example Input: Sentence: 'a boy at a skate park attempts to do tricks on a skateboard'. How many words start with the letter 'a' in the sentence.
Example Output:
5