Yeah as Vapor says for a 120.4 it will be [(120*4)+(10*3)]*120 = 510*120 = 61200mm²

If they used 15mm spacing rather than 25mm then you would just get (120*4)*120 = 480*120 = 57600mm²

So if the PA120.4 follows the original PA120.X design it will have greater facial area than the 140.3 if it conforms to the more common 15mm fan spacing then they will be approximately the same.