Question

A current of 15 A exists in a copper (Cu) wire
which has a diameter of 4 mm.
What is the current density? Each atom of copper has one conductionband, and
the average thermal speed √((k T)/m)
of an
electron is 1 × 106 m/s . The mass den-
sity of Cu is 8.92 g/cm3, its molar mass
is 63.5 g/mol, and Avogadro’s number is
6.02214 × 1023 atoms/mole. The electron
mass is 9.10939 × 10−31 kg, and the resistivity
of copper is 1.7 × 10−8
· m.
charge density is 1.193662073e+06

density of electrons 8.45944705m-3

drift velocity is 8.8814142m/s

i am stuck with this question

What is the average time between collisions of
the “drifting” electrons with the lattice ions?
Answer in units of s.

and

What is their mean free path in this wire?
Answer in units of m.