Ошибка в коде вычисления определителя матрицы

Option Explicit
Dim n, i, j As Single
Dim det As Double
Dim b() As Double
Dim a() As Double
Dim x() As Double
 
Function f(a() As Double) As Double
f = WorksheetFunction.MDeterm(a())
End Function
Private Sub Крамер_Click()
Range("A1:L100").Clear
n = InputBox("Введи число строк матрицы")
ReDim a(n, n), b(n), x(n)
Cells(1, 1) = "Матрица коэффициентов Аi"
Cells(1, 5) = "Вектор  свободных членов Bi"
For i = 1 To n
For j = 1 To n
a(i, j) = InputBox("a(" + Str(i) + "," + Str(j) + ")=", "Введи коэффициенты при неизвестных")
Next j
Next i
For i = 1 To n
b(i) = InputBox("b(" + Str(i) + ")=", "Введи свободные члены")
Next i
For i = 1 To n
For j = 1 To n
Cells(i + 1, j) = a(i, j)
Cells(i + 1, 5) = b(i)
Next j
Next i
det = f(a())
Cells(6, 1) = det
End Sub

a(i, j) = Cdbl(InputBox("a(" + Str(i) + "," + Str(j) + ")=", "Введи коэффициенты при неизвестных"))

ReDim a(n, n), b(n), x(n)

ReDim a(1 to n, 1 to n), b(1 to n), x(1 to n)