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

[Q]: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'
[A]: 1

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

[Q]: Sentence: 'three giraffes are leaning over a fence to eat the tree leaves'. Find frequency of the letter 'i'
[A]:
2