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

Input: Consider Input: Sentence: 'a cat sprawls out and sleeps on its back on a lounge chair with an acorn theme'. Find frequency of the letter 'r'

Output: 3

Input: Consider Input: Sentence: 'a glass vase sits between two statues'. Find frequency of the letter 'o'

Output: 1

Input: Consider Input: Sentence: 'a boy is laying in a bed holding on to his teddy bear'. Find frequency of the letter 'd'
Output: 4