A man sells Rs. 5000, 12% stock at 156 and invests the proceeds partly in 8% stock at 90 and the balance in 9% stock at 108. He thereby increase his income by Rs. 70. How much of the proceeds were invested in each stock?

Selling price of Rs. 5000 stock = $$5000\times\frac{156}{100}=Rs.$$ $$7800$$

Income from stock = $$\frac{12}{100}\times5000=Rs.$$ $$600$$

Now, let investment in 8% stock be Rs. $$x$$ and 9% stock be Rs. $$(7800-x)$$

According to ques,

=> $$\frac{8}{90}\times x+\frac{9}{108}\times(7800-x)=600+70$$

=> $$\frac{8x}{90}+650-\frac{x}{12}=670$$

=> $$\frac{16x-15x}{180}=20$$

=> $$x=3600$$

$$\therefore$$ Amount invested in 8% stock = Rs. 3600 and in 9% stock = Rs. 4200

=> Ans - (A)