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

Sentence: 'a bus with two floors belonging to london country'. Find frequency of the letter 't'
4

Sentence: 'slices of orange are arranged on a plate'. Find frequency of the letter 's'
2

Sentence: 'a couple of people sitting in a living room in pink chairs'. Find frequency of the letter 'r'

2