You will be given a definition of a task first, then some input of the task.
The task is to generate the correct answer for a given math problem.

Problem: a producer of tea blends two varieties of tea from two tea gardens one costing rs 18 per kg and another rs 20 per kg in the ratio 5 : 3 . if he sells the blended variety at rs 21 per kg , then his gain percent is
Output:
12 %