Assume that face value = Rs.100
Dividend per share = Rs.8.5 (as it is 8.5% stock)
By investing Rs.12000, earnings = Rs.750
To get an earning of Rs.8.5, investment required = (12000*8.5)/750 = Rs.136
market value of Rs. 100 stock = Rs.(136- 1/4) = Rs.135.25