A company pays an apprentice a monthly stipend that increases in arithmetic progression. The total stipend paid for the first 6 months is ₹27000 and for the first 12 months is ₹78000.
a. (i) Determine the apprentice’s stipend for the first month and the fixed monthly increment.
b. (ii) Calculate the total stipend the apprentice will receive during months 13 to 18.