Final answer:
To calculate the probability of a certain number of computers being used, more context is needed regarding customer behavior and cafe policy. Typically, combinatorial or statistical methods would be used, assuming proper data.
Step-by-step explanation:
The question pertains to calculating the probability that a given number of computers, denoted as k, are used in an internet cafe when 3 customers arrive at non-overlapping times. If one customer arrives every two minutes on average, then it would take six minutes on average for three customers to arrive. However, the provided information is not sufficient to compute the probabilities directly since the probability of each computer being used depends on varying factors such as customer behavior and cafe policies. To solve similar probability problems, one usually applies combinatorial or statistical methods, perhaps using a Poisson or binomial distribution, contingent on the problem context.