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

Sentence: 'a surfer wipes out on a huge wave'. Find frequency of the letter 'a'
3

Sentence: 'a bird is standing on the ledge of the building'. Find frequency of the letter 't'
3

Sentence: 'a guinea pig is nestled in between several small stuffed animals'. Find frequency of the letter 'n'

5