While shopping online for AA batteries, Masoud found that he could order a pack of 8 batteries for $6.30, a pack of 16 for $13.99, a pack of 20 for $12.32, or a pack of 24 for $13.99. Define a relation using number of batteries as input and price as output. 

(a) What is the domain and range of the relation? 

(b) Express the relation as a set of ordered pairs. 

(c) Express the relation as a mapping. 

(d) Express the relation as a graph.