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: 'four boats on the sand on the beach'. How many words start with the letter 'o' in the sentence.
Example Output: 2

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: 'chinese food including rice and an egg roll is sitting on a red and white plate'. How many words start with the letter 'a' in the sentence.
Example Output:
4