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

Input: Consider Input: Sentence: 'a red stop sign with street signs above it'. Find frequency of the letter 't'

Output: 5

Input: Consider Input: Sentence: 'an airplane is being towed away from the jet bridge'. Find frequency of the letter 's'

Output: 1

Input: Consider Input: Sentence: 'a man with a hat skiing with skis and ski poles'. Find frequency of the letter 'g'
Output: 1