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

Sentence: 'a small boat and a large boat on a river near a city'. Find frequency of the letter 'a'
10

Sentence: 'a full plate of food that includes rice and broccoli and carrots'. Find frequency of the letter 's'
2

Sentence: 'an old wooden table with two wooden chaires next to a clay vase'. Find frequency of the letter 'o'

7