Which of the following statements about Prof. Eric Bradlow's talk on "clumpiness" is correct?

Customers who come in bursts then go away again and again are not profitable.

Traditional RFM metrics are enough to describe arrival patterns of people.

Clumpiness is a new metric which replaces for one of RFM metrics.

Looking at recency, frequency, and monetary value in historical customer data basically ignores the inter$-$arrival times.