Question: Sales let matrix A represent the sales (in thousands of dollars) for the Walbash Company in 2011 in various cities, and let matrix B represent the sales (in thousands of dollars) for the same company in 2012 in the same cities.
(a) Write the matrix that represents the total sales by type and city for both years.
(b) Write the matrix that represents the change in sales by type and city from 2011 to 2012.