Visual basic from excel

For i = 5 To-5 Step-1 a sqr (1) + Cos (3 ) -19 * Next i Identify the execution error below: 1) Subtracting 19 is not appropriate 2) You cannot take the square root of a negative number 3) The step should be positive 1 4) When i gets to O, it can't go to the next i. Dim a As Variant, b As Variant a- Inputbox("Please, enter some value for a.") If IsNumeric(a) True And a 0 Then 2) Dim a As Variant, b As Single 3) Dim a As Single, b As Variant 4) No Change is required. The code will run fine