Buying Time — Robert Greenberger

An investigation into a chroniton disturbance leads the da Vinci to a time-travelling Ferengi named Lant -- one who is going to the past in order to "speculate" and make a fortune. Now Commander Gomez, Lt. Commander Tev, Lt. Commander Corsi, and Cultural Specialist Abramowitz of the S.C.E. must follow Lant into the past in order to preserve the timelines -- and save the future.
But what they find may be more than they can handle, as one Tellarite male and three human females are not as welcome on the Ferenginar of fifteen years ago as they might think...