In one alloy there is 12% chromium while in another alloy it is 8%. 35 kg of the first alloy was melted together with 40 kg of the second one to form a third alloy. Find the percentage of chromium in the new alloy. Choose the correct choice from the following answers
A) 8.8 %  B) 9.75 %  C) 9.2 %  D) 8.6 %  E) 8.4 %

Rationale: "the amount of chromium in the new 35 + 45 = 80 kg alloy is 0.12 * 35 + 0.08 * 45 = 7.8 kg , so the percentage is 7.8 / 80 * 100 = 9.75 % . answer : b ."
Answer: B