Emma Clair is the operations manager for Bert$$s Bistro, which specializes in providing natural products for health$-$conscious individuals. Emma is responsible for compiling, analyzing, and evaluating daily sales numbers to determine the company$$s profitability and forecast production for the next day. Which of the following is an example of a piece of data Emma would be using to successfully perform her job?

a$.$

customer number $15467$ is John Smith

b$.$

best$-$selling product changes when Heidi works as she is the best baker

c$.$

compare the costs of supplies, including energy, over the last five years to determine the best$-$selling product by month

d$.$

best$-$selling product by day