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

Input: Consider Input: Sentence: 'a blue train on a track next to another track'. Find frequency of the letter 'c'

Output: 2

Input: Consider Input: Sentence: 'man in a radio studio wearing a suit in front of a microphone'. Find frequency of the letter 't'

Output: 3

Input: Consider Input: Sentence: 'a dog wearing a yellow hat with a smiley face on it'. Find frequency of the letter 'o'
Output: 3