A wire with diameter $d$ forms part of an electric circuit. A current $I$ flows through the wire, and the charge carriers have a mean drift speed $v$. The wire is then changed to another wire made from the same material, but with diameter $0.5d$. The current is adjusted so that the charge carriers in the new wire have a mean drift speed $3v$. Determine the current in the new wire.
- A$0.75I$
- B$1.5I$
- C$6I$
- D$12I$