Question

Oil used to absorb benzene from gas is to be stripped with steam at P = 1atm to recover the benzene.Equlibrium at the operating temperature is approximated using Henry's Law.When the oil contains 10%mol of benzene,the oil's partial pressure is 5.07kPa.The oil is nonvolatile & enters with 8%mol benzene which 70% from that 8% is to be recovered. Steam leaving is 3%mol benzene.
How many theoretical stages are required?

My question here is,how to approximate the Henry's Law without knowing the temperature? I tried by using the partial pressure of oil given for 90% mol of oil(since 10%mol is benzene).Is my initial step correct? Need help asap,thanks