This is this is my criteria, we will keep that, right now this B by A greater than 0, C by A is greater than 0; and we will discuss that little later after we talk about hydrodynamic derivatives at little more detail. What is B by A, C by A, B A C are all function of Y v Y you know dash N v N v dot dash Y r Y r dot dash N r N r dot dash plus of course, I dash m dash x C dash etcetera these are of course, rigid body parameter, so we are not I mean this is a of course, important, but rigid body parameters, but these are the terms which actually tells me, how a fluid force reacts or acts, if there is a flow around it.