A certain gas obeys the van der Waals equation with a =0.76 m6 Pa mol-2, its volume

Question:

A certain gas obeys the van der Waals equation with a =0.76 m6 Pa mol-2, its volume is found to be 4.00 X 10-4 m3 mol-1 at 288 K and 4.0 MPa. From this information calculate the van der Waals constant b. What is the compression factor for this gas at the prevailing temperature and pressure?