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

Input: Consider Input: Sentence: 'three elephants walk up a dirt trail from the water'. Find frequency of the letter 'l'

Output: 3

Input: Consider Input: Sentence: 'a toasted sub sandwich is next to a salad'. Find frequency of the letter 'a'

Output: 6

Input: Consider Input: Sentence: 'a large pizza sitting on top of a pan covered in cheese'. Find frequency of the letter 't'
Output: 3