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

Sentence: 'a blue train on a track next to another track'. Find frequency of the letter 'c'
2

Sentence: 'a group of people standing on grass with a train in the background'. Find frequency of the letter 'n'
6

Sentence: 'a photo of a kitchen with a fridge and oven and table'. Find frequency of the letter 'd'

3