(SLE) At 20 ºC, the solubility of solid phenanthrene (2) in acetone (1) is 14.5 mol%. If the experimental solubility is to be modeled at other concentrations and temperatures using the one parameter Margules equation, what value of A12 should be used? (Data ΔHfus(1) = 5.69 kJ/mol, ΔHfus(2) =16.46 kJ/mol; Tm(1) =178.15 K, Tm(2) = 372.35 K)