There are too many factors that go into this calculation to give an accurate answer. First, how much cocaine is law enforcement saying was involved? Does this person have any criminal history? Was any firearm involved? Was this person a major or minor participant in the crime? Does this person intend to plead guilty or go to trial? If this person pleads guilty, are they going to cooperate against any other defendant law enforcement is interested in? The answer to these questions could determine whether the person is facing a very small amount of time (possibly even probation or home confinement) to a very long amount of time (up to life in prison).
Your friend should be talking with his criminal defense attorney - wiretaps are long term investigations usually resulting in large drug quantities, all of which leads to significant prison terms. The questions posed by the previous attorney are the key ones to answer but in a federal wiretap case, the overwhelming odds are that your friend is facing significant time.
To add to what the other two attorneys have correctly observed, it should be said that federal judges are supposed be strongly guided by the federal sentencing guidelines, which provide a matrix from which a recommended sentence is supposed to be imposed based upon a number of factors, with the "base offense level" for a drug offense depending on the quantity of drugs the government claims that you distributed or conspired to distribute. Although I agree that the factors can be complicated, an attorney familiar with the sentencing guidelines can calculate the sentencing range under different scenarios, as long as you have some idea as to quantity and prior criminal history. If you don't even know these, then for sure the sentencing range would be probation to life.