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

[EX Q]: Sentence: 'a black animal in dirt area below trees and rocks'. Find frequency of the letter 'n'
[EX A]: 3

[EX Q]: Sentence: 'two little girls playing with a bat and a tennis ball'. Find frequency of the letter 'w'
[EX A]: 2

[EX Q]: Sentence: 'a red chair has a blue towel on it'. Find frequency of the letter 'e'
[EX A]:
3