Answer:
At this partial pressure of oxygen, Mb would be almost completely saturated but Hb would not.
Explanation:
The oxygen saturation curves for Mb and Hb are quite different. The curve for Mb is hyperbolic while that for Hb is sigmoidal.
Mb reaches oxygen saturation before Hb.
Thus, at a partial pressure of 40 mmHg, Mb is almost completely saturated but Hb is not.