A start-up company built a database of customers and sales information. for each customer, it recorded the customer's name, zip code, region of the country (east, south, midwest, west), date of last purchase, amount of purchase (in dollars), and item purchased. (a ) identify whether the data are cross sectional or a time series. (b )give a name to each variable and indicate if the variable is categorical, ordinal, or numerical (if a variable is numerical, include its units if possible). (c )list any concerns that you might have for the accuracy of the data.