0.3 g of acetic acid (Molar mass = 60 g mol\(^{-1}\)) dissolved in 30 g of benzene shows a depression in freezing point equal to 0.45°C. Calculate the percentage association of acid if it forms a dimer in the solution.
(Given: \( K_f \) for benzene = 5.12 K kg mol\(^{-1}\))