There's only two items. Try the three possible ways.
Unfortunately, we don't know the actual price of the item. All we know is the final invoice.
Actual Price = P
Both Discount and GST apply to total.
Discount: P*0.09 = D
GST: P*0.10 = G
Paid: P - D + G = 4007.70
Let's try the discount first, then apply the GST
Discount: P*0.09 = D
Subject to GST: P - 360.69 = S
GST: S*0.10 = G
Paid: P - D + G = 4007.70
Only one left. Add the GST and then apply the discount.
GST: P*0.10 = G
Amount subjec to to discount: P + G = T
Discount: T*0.09 = D
Paid: P - D + G = 4007.70
That may actually be illegal.
One of those should work.