A video magazine distributor made 3500 copies of the March issue of the magazine at a cost of Rs. 350000. He gave 500 cassettes free to some key video libraries. He also allowed a 25% discount on the market price, of the cassette and gave one extra cassette free with every 29 cassettes bought at a time. In this manner, he was able to sell all the 3500 cassettes that were produced. If the market price of a cassette was Rs. 150, then what is his gain or loss percent for the March issue of video magazine? a. `10 %` gain b. `25%` loss c. `40%` gain d. `6.8%` loss