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 cat sitting on a pan in an oven'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a plate has ribs broccoli and mashed potatoes on a plate'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a bench with a broken slat overlooking the water'. How many words start with the letter 'b' in the sentence.
Example Output:
2