In this task, you need to count the number of times the given letter appears in the given sentence.

Input: Consider Input: Sentence: 'a girl that has a kite in the air'. Find frequency of the letter 'r'

Output: 2

Input: Consider Input: Sentence: 'a young boy wearing black and holding a skateboard on the sidewalk'. Find frequency of the letter 'n'

Output: 5

Input: Consider Input: Sentence: 'people standing around in front of a bike store'. Find frequency of the letter 'a'
Output: 3