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

Example Input: Sentence: 'a family sitting at a table in a restaurant looking at their phones'. Find frequency of the letter 't'
Example Output: 8

Example Input: Sentence: 'cars parked outside if a retail store'. Find frequency of the letter 'd'
Example Output: 2

Example Input: Sentence: 'a packed lunch has a rice dish, vegetables, and a peach'. Find frequency of the letter 'h'
Example Output:
4