Two oils are tested to establish their viscosity index. Oil "A" and Oil "B" have their viscosity measured at temperatures of 40C and 100C. Oil "A" has a viscosity of 80Cst at 40C and 8Cst at 100C. Oil "B" has a viscosity of 90Cst at 40C and 15Cst at 100C. Which oil has the higher viscosity index?