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

Sentence: 'a double decker bus with a lot of people on board'. Find frequency of the letter 'l'
3

Sentence: 'the skateboarder has on red and black sneakers and is riding a skateboard'. Find frequency of the letter 'g'
1

Sentence: 'a plate topped with pasta and and onions'. Find frequency of the letter 't'
4