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 using a video game controller in a room'. Find frequency of the letter 'n'

Output: 4

Input: Consider Input: Sentence: 'an empty clean kitchen with island, marble countertops , stove and cabinetry'. Find frequency of the letter 'l'

Output: 3

Input: Consider Input: Sentence: 'a woman is smiling as she stands in her kitchen'. Find frequency of the letter 'i'
Output: 5