instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'two metal  benches on an empty train platform'. Find frequency of the letter 'n'
answer:
4


question:
Sentence: 'a man hitting a tennis ball with a tennis racquet'. Find frequency of the letter 't'
answer:
6


question:
Sentence: 'people flying kits in a grassy field, with one multicolored kite on the ground'. Find frequency of the letter 'f'
answer:

2