How to solve this one manually without the use of a financial calculator.

5-7 RETURN EARNED ON ANNUITY Lin Shan is about to retire and is exploring the possibility of investing a lump sum in an annuity so that she gets 50% of her last drawn salary at the end of every month for 15 years. She esti- mates her last-drawn salary to be 60,000. The quotation she obtained from Ping Tan Insurance requires her to invest a lump sum of 1 million. Calculate the return that Lin Shan is earning on her annuity