[UPSC CSE 1986] Thermodynamics (Q238, 20M)

Consider the following equation of state for a gas: $P = \frac{RT}{v-b} - \frac{a}{Tv^{2}}$ where $a$ and $b$ are constants and other symbols have their usual meaning. Find the values of $P_{c}$ , $T_{c}$ and $V_{c}$ in terms of $a$ and $h$ at the critical point.