Suppose that General Manager of Toyota estimated the following regression equation for demand of his product
Q1 = 100000-100Pt + 2000N + 50I + 30Ph - 1000Pg + 3.4A

Where Q1 = quantity demanded of Toyota per year
Pt = Price of toyota car
N = Population of country
I = per capita disposable income
Ph = Price of Honda
Pg= Price of Gasoline
A = Advertising expenditure by toyota company

a) Indicate the change in the number of toyota purchased per year Q1 for each unit change in the independent or explanatory variable.
b) Derive the equation for the demand curve for Toyota and plot this demand curve