instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'a herd of horses standing next to each other on a field'. Find frequency of the letter 'r'
answer:
3


question:
Sentence: 'a train station with a train pulling into the platform'. Find frequency of the letter 'i'
answer:
6


question:
Sentence: 'an elephant walking on grassy area next to trees'. Find frequency of the letter 'o'
answer:

2