An unknown compound's (+)-isomer has a specific rotation of +148^o. Calculate its observed rotation if a mixture contains 60.0 % (-)-isomer and 40.0 % (+)-isomer.

• A. Observed rotation = -148
• B. Observed rotation = +0.20
• C. Observed rotation = +0.60
• D. Observed rotation = -29.6

Answer: (D)