See the picture attached, find the molar volume of Mixture methane (1) + n-Butane (2) at P = 101 bar, T= 511.15 K with mole numbers given.
you can use the a1,b1, and a2, b2 numbers to get the mixture parameters am, and bm.
Use Goal-Seek in Excel to find the molar voluem, v in Liter/gmol.
Enter the value of v below!