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

Input: Consider Input: Sentence: 'a black animal in dirt area below trees and rocks'. Find frequency of the letter 'n'

Output: 3

Input: Consider Input: Sentence: 'a man walking a large elephant down a dirt road'. Find frequency of the letter 'g'

Output: 2

Input: Consider Input: Sentence: 'a cat that is sitting on a suitcase'. Find frequency of the letter 'a'
Output: 5