instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a stop sign near a rail road crossing sign'. Find frequency of the letter 'g'
answer:
3


question:
Sentence: 'a man riding on the back of a white horse next to other horses'. Find frequency of the letter 'o'
answer:
6


question:
Sentence: 'a street scene looking at the back of the stop sign'. Find frequency of the letter 't'
answer:

6