Hi,
please take a look at this problem:

A coaxial line is made of two perfect conductors. The inner cylinder has radius a and the radius of the outer one is b. The outer conductor is grounded.
Suppose that the inner conductor carries 1[C] of charge per meter of its length, that is its equivalent line charge density is ρlo=1[C/m].

a- Find the potential difference between the two conductors.
b- What is the potential of the outer conductor?
c- What is the potential of the inner conductor?


a-
V= (Q/4*pi* ε0)( 1/a-1/b)

with Q=?

b-
Vb=0[V]

c-

Va=(Q/4*pi*ε0)(1/a)

I have some issue with the value of Q. since the length is not specified should Q be Q=1*L=L (Length)??