A van der Waals gas has a value of z = 1.00061 at 410. K and 1 bar and the Boyle temperature of the gas is 195 K. Because the density is low, you can calculate V_m from the ideal gas law. Use this information and the result of Problem 7.28, z ≈ 1 + (b − a/RT)(1/V_m), to estimate a and b.