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

Sentence: 'two people under an umbrella while walking down a sidewalk'. Find frequency of the letter 'i'
3

Sentence: 'a woman holds some baked goods at the convention'. Find frequency of the letter 'd'
3

Sentence: 'one woman holding a video game controller and standing next to another woman'. Find frequency of the letter 't'

5

