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

Input: Consider Input: Sentence: 'a piece of meat covered in ketchup next to a hamburger on a green plate'. Find frequency of the letter 'g'

Output: 2

Input: Consider Input: Sentence: 'a group of men standing on the side of a boat'. Find frequency of the letter 'o'

Output: 5

Input: Consider Input: Sentence: 'conference room with big screen on wall and table in the center with a workstation on the side'. Find frequency of the letter 'h'
Output: 4