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: 'person in profile and sunlight at a barred window'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a picture of a zebra that is walking in the grass'. How many words start with the letter 'z' in the sentence.
Example Output: 1

Example Input: Sentence: 'a close up of a slice of pizza on a box'. How many words start with the letter 'o' in the sentence.
Example Output:
3