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: 'mounds of plantains are on display at market stalls'. How many words start with the letter 'm' in the sentence.
Example Output: 2

Example Input: Sentence: 'zebras and antelopes in a field of dried grass'. How many words start with the letter 'a' in the sentence.
Example Output: 3

Example Input: Sentence: 'a group of four people are riding a ski lift as they ride over the snowy mountain'. How many words start with the letter 'a' in the sentence.
Example Output:
4