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

Input: Consider Input: Sentence: 'a woman walking with a child that is in a wheelchair'. Find frequency of the letter 'k'

Output: 1

Input: Consider Input: Sentence: 'a couple of men standing inside of a liquor store'. Find frequency of the letter 'p'

Output: 1

Input: Consider Input: Sentence: 'a cake is designed with a train theme'. Find frequency of the letter 'r'
Output: 1