Rate equation question

The reaction between two different compounds, C and D, is studied at a given temperature.
The rate equation for the reaction is found to be
rate = k[C][D]
2
(i) When the initial concentration of C is 4.55 × 10–2 mol dm–3 and the initial
concentration of D is 1.70 × 10–2 mol dm–3, the initial rate of reaction is
6.64 × 10–5 mol dm–3 s–1
.
Calculate the value of the rate constant at this temperature and deduce its units.
Calculation ............................................................................................
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Units of rate constant ............................................................................
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(ii) The experiment in part (i) is repeated at the same temperature but after the addition
of extra solvent so that the total volume of the mixture is doubled.
Deduce the new initial rate of reaction.
Im struggling on part ii could someone please explain why the answer is 8.3x10-6 ??
I divided the concentrations by 2 however i did not get the correct answer.
PS: k=5.05