now actually if your l I know, now rho I have to know rho this is the I have to find out rho ok, this task I have to do, I have to find out rho now if say I know rho either it is supplied or I will measure it, this part I know, this part also I know, and this also I know, x, y is unknown to me.
हे मला माहित आहे, हे पण दिलेय, X आणि Y मला माहित नाहीत.