If a company spends r million dollars on research, it sales will be s million dollars, where r and s are related by $=3-55. (a) Find ds/dr by implicit differentiation and evaluate it at r = 4, s = 3. [Hint: Differentiate the equation with respect to r.] ds dr (b) Find dr/ds by implicit differentiation and evaluate it at r = 4, 5 = 3. [Hint: Differentiate the original equation with respect to s.] dr ds (c) Interpret your answer to part (a) as a rate of change. Given ds/dr = n, this means that the rate of change of sales with respect to research expenditures is n, so that increasing research by one million dollars will increase sales by about n million dollars (at these levels of r and s). O Given ds/dr = n, this means that the rate of change of research expenditures with respect to sales is n, so that increasing sales by one million dollars will increase research by about n million dollars (at these levels of r and s). O Changing research will not affect sales. Interpret your answer to part (b) as a rate of change. O Changing sales will not affect research. O Given dr/ds=m, this means that the rate of change of sales with respect to research expenditures is n, so that increasing research by one million dollars will increase sales by about m million dollars (at these levels of r and s). O Given dr/ds = m, this means that the rate of change of research expenditures with respect to sales is m, so that increasing sales by one million dollars will increase research by about m million dollars (at these levels of r and s).