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

Input: Consider Input: Sentence: 'a girl playing with a frisbee while people watch'. Find frequency of the letter 'e'

Output: 5

Input: Consider Input: Sentence: 'a woman fully dressed as a geisha'. Find frequency of the letter 'm'

Output: 1

Input: Consider Input: Sentence: 'a man siting down on the snow with his feet on a snowboard'. Find frequency of the letter 't'
Output: 4