QUESTION 19 A study estimates the demand for over-the -counter cough medicines to be log Q = 0.885-0.744 log(P) -0.50 log(INC) + 0.253 log(ADV) -0.30 log(PHYSP) R2 = 0.4, Adj. R2 = 0.3 where Q = Annual dosages demanded of cough and cold medicines P = Price per dosage of cough and cold medicines INC = Average income of buyers ADV = Advertising expenditure s on cough and cold medicines PHYSP = Market price of physician visit What percentage of the variation in dosages remains unexplained? O a. 40% b. 60% O c. 30% O d. 70%