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

[EX Q]: Sentence: 'vanity sitting atop a base with two doors and a mirror overhead'. Find frequency of the letter 'n'
[EX A]: 3

[EX Q]: Sentence: 'a woman holds some baked goods at the convention'. Find frequency of the letter 'd'
[EX A]: 3

[EX Q]: Sentence: 'a bird sits on a branch in a tree'. Find frequency of the letter 'i'
[EX A]:
3