A Student Measured the Optical Activity of an Unknown Sugar

A student measured the optical activity of an unknown sugar at two different concentrations. The results of his measurements are shown below. Given that the sample cell had a path length of 10.0 cm, calculate the specific rotation for the unknown sugar. (Hint: Consider each measurement of plane polarized light has a true reading and a "ghost" reading 180° from the true reading) .

A) -10.5^∘
B) +25.6^∘
C) +79.5^∘
D) -105^∘
E) +256^∘