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

Input: Consider Input: Sentence: 'a chair and umbrella on a sandy beach'. Find frequency of the letter 's'

Output: 1

Input: Consider Input: Sentence: 'two baseball players high five each other during a game'. Find frequency of the letter 'y'

Output: 1

Input: Consider Input: Sentence: 'this giraffe is the grass he is an adult giraffe'. Find frequency of the letter 't'
Output: 3