how can i eliminate the error of "Use of unassigned local variable"

Hie i was programming c# and I am having issue getting error that use of unassigned variable where I have already declared the variable. Please help. I have even done building solution in visual studio 2010.

    public decimal FinishCost 
     {
        get {
            decimal fnCost;

            if (exteriorFinishChosen == ExteriorFinish.None) 
            {
                fnCost = Finish.None;
            }

            else if (exteriorFinishChosen == ExteriorFinish.Standard)
            {
                fnCost = Finish.Standard;
            }
            else if (exteriorFinishChosen == ExteriorFinish.Pearlized)
            {
                fnCost = Finish.Pearlized;
            }
            else if (exteriorFinishChosen == ExteriorFinish.Custom)
            {
                fnCost = Finish.Custom;
            }
            return fnCost;
        }
    }