45.White to move

In the position above it seem like an equal position for both side.The question is

a)What is the best continuation possible for White to gain an advantage and lead to a winning position?

Thanks again to Eugene for solving problem 44 by 1.Ra8! There's no square for Black Queen to escaped if 1....Qh7 2.Bg6 Qxg6 3.Ra6+ Kb5 4.Rxg6, 1...Qxa8 2.Bf3+ Kb5 3.Bxa8, 1....Qd5 2.Bf3 ,1...Qe6 2.Ra6+,1...Qc4 2.Rc8+,1....Qa2 2.Rxa4 Qxa4(...Qg8 3.Ra8) 3.Be8+