=ЕСЛИ(B4>20,9;B4*C2;ЕСЛИ(И(B4>10;B4<20,1);B4*B2;ЕСЛИ(B4<10,1;B4*A2)))

Sub psk()
    Dim dates()
    Columns("A:A").Select
    dates() = Application.Transpose(Range(ActiveCell, Cells(Rows.Count, ActiveCell.Column).End(xlUp)))

    Dim summa()
    Columns("B:B").Select
    summa = Application.Transpose(Range(ActiveCell, Cells(Rows.Count, ActiveCell.Column).End(xlUp)))
    
    Dim m As Integer
    m = UBound(dates)
           
    bp = 30
    cbp = Round(365 / bp)
    
    ReDim Days(m)
    For k = 2 To m
        Days(k) = dates(k) - dates(2)
    Next
    
    ReDim e(m)
    ReDim q(m)
    
    For k = 2 To m
        q(k) = Days(k) \ bp
        e(k) = (Days(k) Mod bp) / bp
    Next
    
    i = 0
    x = 1
    x_m = 0
    s = 0.000001
    Do While x > 0
        x_m = x
        x = 0
        For k = 2 To m
            x = x + summa(k) / ((1 + e(k) * i) * ((1 + i) ^ q(k)))
        Next
        i = i + s
    Loop
    If x > x_m Then
        i = i - s
    End If
    
    psk = Round(i * cbp, 5)
    Cells(3, 7).Value = psk   
End Sub