In a certain PLMN,an average subscriber makes 5 calls during office hours （8 AM - 6 PM)

In a certain PLMN,an average subscriber makes 5 calls during office hours (8 AM - 6 PM).It is known that in a certain cell area,there are going be 1000 subscribers,at any given hour,during these office hours.Assuming that a subscriber’s conversation lasts for 100 seconds,how many TRXes are needed in this cell to provide a grade of service of 2%？ （）

A.2

b.3

c.4

d.There is not enough information given for an exact answer.