Condenser A has a capacity of $15\,\mu\text{F}$ when it is filled with a medium of dielectric constant $15$. Another condenser B has a capacity $1\,\mu\text{F}$ with air between the plates. Both are charged separately by a battery of $100\,\text{V}$. After charging, both are connected in parallel without the battery and the dielectric material being removed. The common potential now is