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

Ex Input:
Sentence: 'the meal is served and ready to be eaten'. Find frequency of the letter 'e'

Ex Output:
8


Ex Input:
Sentence: 'a street at night with trees and streetlights on'. Find frequency of the letter 't'

Ex Output:
9


Ex Input:
Sentence: 'a rusted out dairy truck sitting in a  field with an old rubber tire leaning up against it'. Find frequency of the letter 'n'

Ex Output:

6