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

[Q]: Sentence: 'a gray airplane with metal petals on the wings takes off from an airport'. Find frequency of the letter 'i'
[A]: 4

[Q]: Sentence: 'there is a baseball game on and a few people are watching'. Find frequency of the letter 'i'
[A]: 2

[Q]: Sentence: 'a snowboarder next to a tube for tricks'. Find frequency of the letter 'o'
[A]:
4