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

Input: Consider Input: Sentence: 'a man with a large grey and black beard and glasses and a tie'. Find frequency of the letter 'e'

Output: 5

Input: Consider Input: Sentence: 'a dog is shown sitting on rocks by the beach'. Find frequency of the letter 'a'

Output: 2

Input: Consider Input: Sentence: 'a banana that was placed under a purple pillow'. Find frequency of the letter 'n'
Output: 3