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

Example Input: Sentence: 'a room with a big screen television and a couch'. Find frequency of the letter 'h'
Example Output: 2

Example Input: Sentence: 'two people in a snowy place near a wooden fence'. Find frequency of the letter 'n'
Example Output: 5

Example Input: Sentence: 'a jacked up pickup truck  drives down a city road'. Find frequency of the letter 'd'
Example Output:
4