A man's income is increased by Rs. 1200 and at the same time, the rate of tax to be paid is reduced from 12% to 10%. He now pays the same amount of tax as before. What is his increased income if 20% of his income is exempted from tax in both cases? `R s .4500` b. `R s .6300` c. `R s .6500` d. `R s .7200`