A departmental store receives a shipment of 1000 pens, for which it pays Rs. 9000. The store, sells the pens at a price 80 percent above cost for one month, after which it reduces the price of the pens to 20 percent above cost. The store, sells 75 percent of the pens during the first month and percent of the 50. remaining pens afterwards. How, mach gross income did the sales of the pens generate? `R s .10000` b. `R s .10800` c. `R s .12150` d. `R s .13500`