The weekly stipend paid to a trainee in a workshop forms an arithmetic progression. The trainee receives a total of Rs. 520 in the first four weeks and a total of Rs. 4000 in the first sixteen weeks.
(i) Taking the first week’s stipend as a and the weekly increase as d, frame two equations connecting a and d with the information given above.
(ii) Solve the equations obtained in part (i) to find the values of a and d.
(iii) Calculate the amount the trainee will receive in the 20th week.