The p-v-T relation

Question

Nitrogen at an initial state of 10 bar, 1m³ and 300 K is expanded isothermally to a final volume of 2m³. The p-v-T relation is $\left ( p+\frac{a}{v^{2}} \right )$  v = RT, where a>0. The final pressure                                                                        

      (a) will be slightly less than 5 bar

      (b) will be slightly more than 5 bar

      (c) will be exactly 5 bar

      (d) cannot be ascertained in the absence of the value of a.