Barbata invests $2400 in the National Bank at 4%. How much additional money must she invest at 8% so that the total annual income will be equal to 6% of her entire investment?
Select.
A) 1200
B) 3000
C) 2400
D) 3600
E) 2450

Rationale: "let the additional invested amount for 8 % interest be x ; equation will be ; 2400 + 0.04 * 2400 + x + 0.08 x = 2400 + x + 0.06 ( 2400 + x ) 0.04 * 2400 + 0.08 x = 0.06 x + 0.06 * 2400 0.02 x = 2400 ( 0.06 - 0.04 ) x = 2400 * 0.02 / 0.02 = 2400 ans : c"
Answer: C