Students of Class VI in a school were given a task to count the number of articles made of different materials in the school. The information collected by them is represented as follows:
Observe the pictograph and answer the following questions: (a) Which material is used in maximum number of articles? (b) Which material is used in minimum number of articles? (c) Which material is used in exactly half the number of articles as those made up of metal? (d) What is the total number of articles counted by the students?