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

[Q]: Sentence: 'two men in black wet suits beside a white surfboard'. Find frequency of the letter 'e'
[A]: 5


[Q]: Sentence: 'man in air skateboarding on street with building'. Find frequency of the letter 't'
[A]: 4


[Q]: Sentence: 'a group of cows that are standing in the grass'. Find frequency of the letter 'g'
[A]:
3