function fdc(order::Int64)

    # This function calculate FD coefficient for spatial finite difference
    # Currently we define the coefficient as the one for the 4th order
    # search "Finite difference coefficient" online for different order

    if order == 4
        FDC = [1/24, -9/8, 9/8, -1/24] # Finite-Difference Coefficient
        else error("please choose choose 4")
    end
    return FDC
end
