Suppose you have the following regression equation where PROD = output produced per month, LHR = labor hours paid per month, and QUAL = quality of raw materials purchased within the month, and T=trend variable: Prod = ß0 + ß1LHR + ß2QUAL + ß3T. If ß3 = 3.5 and is significantly different from zero, this result indicates
A) an increase in labor efficiency.
B) an increase in the quality of raw materials used in the production process.
C) an increase in labor efficiency or the quality of raw materials or both.
D) an increase in production efficiency holding constant labor efficiency and material quality.
E) an increase in production efficiency due to an increase in labor efficiency or quality of materials or both.