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 yellow grey and white bird on a small group of twigs'. How many words start with the letter 'b' in the sentence.
Example Output: 1

Example Input: Sentence: 'a large group of men with bats in a dugout'. How many words start with the letter 'g' in the sentence.
Example Output: 1

Example Input: Sentence: 'a vintage looking image of a horse and cart in a town'. How many words start with the letter 'o' in the sentence.
Example Output:
1