Assume that the 6 dimensions in both vectors represent 6 different items found in a store. Each vector represents a customer transaction, indicating whether a customer has purchased a particular item (1) or not (0). We are interested in developing a customer similarity metric, which considers two customers similar when they both purchase the same item. The similarity metric does not need to consider the case when both customers do not purchase any particular item. Which of the above two coefficients should we use and why