Creating a Matrix Using NumPy Arrays

Before we can start working with NumPy, we'll need to make sure that we have it installed. Utilize pip to install the numpy package.

Since we have the sales numbers for each item from each store, we can create an array for each store's sales that can later be used to make calculations. We need to make sure that we're putting the sales numbers for each item in the same position for each of our stores' arrays. Create a 4 item array for each store, placing the number of sales for each item in the order of pens, notebooks, staplers, and backpacks.

Because we have 4 different items, each stores' sales are stored as a 4 item, one-dimensional array, or a 1x4 matrix. We can use matrix multiplication to calculate the revenue for a store by multiplying that array with a 4x1 matrix where each row is the price for the corresponding column item in the sales arrays. Combine all of our sales variables into a single 4x4 matrix so that we can calculate the revenue for all of the stores at the same time, and create a 4x1 prices matrix that has the prices list from top to bottom for pen, notebook, stapler, and backpack.

Calculate the dot product of these two matrices to get the revenue for each store and then utilize those values to calculate the total revenue.