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 couple of kids are sitting in the grass'. How many words start with the letter 'a' in the sentence.
Example Output: 2

Example Input: Sentence: 'this photo shows four copies of the same fire hydrant'. How many words start with the letter 't' in the sentence.
Example Output: 2

Example Input: Sentence: 'a grey cat starring at a hand with a donut'. How many words start with the letter 'a' in the sentence.
Example Output:
4