A student decides to save money every week. She saves Rs 100 in the first week and increases her saving by Rs 10 each subsequent week, so that the weekly amounts form an arithmetic progression.
(i) How much will she save in the 40th week?
(ii) Find the total amount she will have saved by the end of 52 weeks.
(iii) After how many weeks will her cumulative savings first exceed Rs 15,000? Show your complete working.