What observed rotation is expected when a (7.91x10^-1) M solution of (R)-2-butanol (mw = 74.12 g/mol) is mixed with an equal volume of a 0.740 M solution of racemic 2-butanol, and the resulting solution is analyzed in a sample container that is 1 dm long? The specific rotation of (R)-2-butanol is -13.9 degrees mL g^-1 dm^-1.