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

Sentence: 'a person on a surfboard in the surf of a wave'. Find frequency of the letter 's'
3

Sentence: 'a plate of food, with broccoli and nuts'. Find frequency of the letter 'b'
1

Sentence: 'airplanes are shown both at the gate and on the runway'. Find frequency of the letter 'a'

7