Answer the following questions related to the basic terminology of arithmetic sequences and series.
a. (i) Define a sequence and a series in the context of real numbers.
b. (ii) What is meant by a finite sequence? Give one illustrative example. What is meant by an infinite sequence? Give one illustrative example.
c. (iii) State the condition under which a sequence becomes an arithmetic progression (AP). Further, write the first four terms of an AP whose first term is 7 and common difference is –3.