In a school, students thought of planting trees in and around the school to reduce air pollution. It was decided that the number of trees that each section of each class will plant, will be the same as the class in which they are studying, e.g., a section of class I will plant one tree, a section of class II will plant two trees and so on till class XII. There are three sections of each class. Find(a) How many trees will be planted by the students?

(b) Which mathematical concept is used in above problem?

(c) Which value is depicted in this problem