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

Sentence: 'a woman in a messy kitchen with a child'. Find frequency of the letter 'a'
4

Sentence: 'girls posing of a picture one holding a tennis racket the other wearing a crown'. Find frequency of the letter 'g'
4

Sentence: 'the kitchen area in this house is very nicely organized'. Find frequency of the letter 'n'
4