TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'girls posing of a picture one holding a tennis racket the other wearing a crown'. Find frequency of the letter 'g'

SOLUTION: 4

PROBLEM: Sentence: 'two zebras feed on a plant through some wire mesh'. Find frequency of the letter 'o'

SOLUTION: 4

PROBLEM: Sentence: 'several airplanes parked at an airport equipped with generators'. Find frequency of the letter 'a'

SOLUTION:
8