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: 'the passengers are going up the step in to the plane'. How many words start with the letter 't' in the sentence.
Example Output: 4

Example Input: Sentence: 'a group of people standing around an airplane on top of a field'. How many words start with the letter 'a' in the sentence.
Example Output: 5

Example Input: Sentence: 'two bear statues one is sitting on a thank you sign'. How many words start with the letter 'b' in the sentence.
Example Output:
1