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 riding a skateboard down a street'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a bus and two cars are going down a two way street'. How many words start with the letter 't' in the sentence.
Example Output: 2

Example Input: Sentence: 'a grain with broccoli on a white plate'. How many words start with the letter 'o' in the sentence.
Example Output:
1