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 skateboarder doing a trick at a skate park'. How many words start with the letter 'a' in the sentence.
Example Output: 4

Example Input: Sentence: 'a woman in a white tshirt and black pants skiing down a small hill'. How many words start with the letter 'd' in the sentence.
Example Output: 1

Example Input: Sentence: 'the elephants are waiting patiently for feeding time'. How many words start with the letter 'p' in the sentence.
Example Output:
1