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

Example Input: Sentence: 'the bathroom is in need of remodel'. Find frequency of the letter 'e'
Example Output: 5

Example Input: Sentence: 'a plastic tray that has different foods inside of it'. Find frequency of the letter 't'
Example Output: 6

Example Input: Sentence: 'a plate of food on a table near a drink'. Find frequency of the letter 'a'
Example Output:
6