Calculating weight percentage of MTBE (methyl-tert-butyl ether) in gasoline so as to achieve specific desired oxygen content?

If gasoline had a hypothetical chemical formula of C8H17, and we knew the chemical formula of MTBE as CH3OC4H9, what weight (actual weight and percent by weight) of MTBE should be in the gasoline to achieve a final gasoline blend that has 2.7% oxygen by weight? Assume the densities of gasoline and MTBE equivalent at 0.75 g per cm3. I do not know if the above assumption concerning gasoline and MTBE density is correct? Above is how the example question I am working on reads --- however, might it be that the gasoline before MTBE and then after adding MTBE have the same density of .75 g/cm3??? Also, what is the stoichiometric air to fuel ratio (lb to lb) for the above final mixture of gaso... click for more