When a marketer wants to test whether a new campaign is effective, she or he conducts a pilot test to see how the new campaign works to engage and motivate customers and potential customers. Which of the metrics listed below are PERFORMANCE metrics.

Question $4$Select one or more:

a$.$

Sales gains from the period of time immediately before the campaign starts to the period of time when the campaign ends.

b$.$

The number of new customers obtained.

c$.$

The percentage of existing customers whose purchases the brand during the campaign were greater than their purchases prior to the campaign.

d$.$

The number of visitors who came to the brand's website.

e$.$

The number of likes for the campaign's social media posts.