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 man touching a bird on top of a cage'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'the colorful fruit is laid out in boxes'. How many words start with the letter 'i' in the sentence.
Example Output: 2

Example Input: Sentence: 'a herd of elephants with large and small elephants at the zoo'. How many words start with the letter 'a' in the sentence.
Example Output:
3