Now i realise in this example i achieved a B rank. I couldn't redo the mission as i forgot to save before the mission started. Heres how you achieve your A rank:
As long as you keep at least 1 extra commander point from your second turn you'll get an A rank. This is so you can use the edelweiss three times to destroy the tank in your 3rd turn. I'd also recommend you move Alicia next to the tower watchmen to aid to their interception fire.