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 mirror a sink a toilet  and a blue basket'. How many words start with the letter 'a' in the sentence.
Example Output: 5

Example Input: Sentence: 'a woman in a black tennis outfit playing tennis on a red clay court'. How many words start with the letter 'r' in the sentence.
Example Output: 1

Example Input: Sentence: 'a woman is typing on her cellphone at a table'. How many words start with the letter 'a' in the sentence.
Example Output:
3