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

[EX Q]: Sentence: 'a lady mixes some things in a blender as people look on'. Find frequency of the letter 'i'
[EX A]: 3

[EX Q]: Sentence: 'a group of people seated in chairs together and facing the same direction, with one man holding a soccer ball in his hands'. Find frequency of the letter 'm'
[EX A]: 2

[EX Q]: Sentence: 'a person riding a skateboard down an empty brick sidewalk'. Find frequency of the letter 'd'
[EX A]:
4