Cost Optimisation Calculation

Try this UDF.

Enter in cell:- =Vol(A1) where "A1" is the cell with the "x" (i.e 150)

Function Vol(Rng As Range) As String
Dim Num As String
  Select Case Rng
  Case Is <= 30: Num = "1x30"
  Case Is < 66: Num = "2x30"
  Case Is >= 66
        Num = Int(Rng / 66) & "x66"
        If Not Int(Rng / 66) = Rng / 66 Then
            Num = Num & " + " & IIf(Rng Mod 60 <= 30, "1x30", "2x30")
        End If
  End Select
Vol = Num
End Function