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

Input: Consider Input: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'

Output: 1

Input: Consider Input: Sentence: 'a display case filled with lots of different clocks'. Find frequency of the letter 'w'

Output: 1

Input: Consider Input: Sentence: 'two trains on the same tracks that are facing each other'. Find frequency of the letter 't'
Output: 7