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

Input: Consider Input: Sentence: 'a stop sign near a rail road crossing sign'. Find frequency of the letter 'g'

Output: 3

Input: Consider Input: Sentence: 'a knife a cutting board some bananas and a toaster'. Find frequency of the letter 'i'

Output: 2

Input: Consider Input: Sentence: 'a white plate topped with a sandwich and a slice of salami'. Find frequency of the letter 'i'
Output: 5