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

[EX Q]: Sentence: 'a river with a long dragon boat in it and rowers on the boat in sets of two, along with two other people'. Find frequency of the letter 'h'
[EX A]: 4

[EX Q]: Sentence: 'a gray elephant is in a grassy field'. Find frequency of the letter 'e'
[EX A]: 3

[EX Q]: Sentence: 'a freight train passing through the outskirts of a  city'. Find frequency of the letter 't'
[EX A]:
7