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: 'an airplane as it is taking off and is ascending into space'. How many words start with the letter 'a' in the sentence.
Example Output: 5

Example Input: Sentence: 'a person with blue sneakers and jeans with one foot on a skateboard and the other foot on the ground'. How many words start with the letter 'o' in the sentence.
Example Output: 4

Example Input: Sentence: 'a yellow and silver bus behind a fork lift'. How many words start with the letter 'y' in the sentence.
Example Output:
1