Using data collected from 1929 to 1941, Richard Stone determined that the yearly quantity Q of beer consumed in the United Kingdom was approximately given by the formula Q = f (m, p, r, s), where f (m, p, r, s) = (1.058)m^0.136p^-0.727r^0.914s^0.816 and m is the aggregate real income (personal income after direct taxes, adjusted for retail price changes), p is the average retail price of the commodity (in this case, beer), r is the average retail price level of all other consumer goods and services, and s is a measure of the strength of the beer. Determine which partial derivatives are positive and which are negative, and give interpretations. (For example, since

people buy more beer when the prices of other goods increase and the other factors remain constant.)

af r 0,