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

Sentence: 'a picture of two computers on a table'. Find frequency of the letter 'r'
2

Sentence: 'a golden haired dog looking out of an open window'. Find frequency of the letter 'd'
4

Sentence: 'a cat on the curb in front of a cars bumber'. Find frequency of the letter 'c'

3