Determine the concentration of the analyte using the laboratory data

HCL: Initial Volume 13.6mL, Final Volume (mL) blank, Concentration (M) unknown.
Ca(OH)2: Initial Volume 0.1mL, Final Volume 18.8mL, Concentration 0.01M

I've gotten to moles of HCL
2HCL + Ca(OH)2 -> 2H2O+CaCl2

18.8(0.1)(2) = moles of HCL

but I don't see a way to get the final concentration of HCL, because you would need at least one variable (final vol or final concentration) to find the other.

The hint it gives me is "You need to find the difference in volume and use that as your V for calcium hydroxide"