Along the lines of what Kyle is saying, nobody is going to do the calculation for you, but I think the answer is conceptually more comlpicated that the other two clear regimes (supersonic and subsonic).
Supersonic flight and subsonic flight incur two different kind of airflow. Trying to travel at exactly the speed of sound would present a lot of difficulties in the first place, because the speed of sound is sensitive to air composition and temperature, which will change as you traverse the sky.
Regardless, this speed of travel, near Mach 1, is called "transonic" and encompasses a range where both supersonic and subsonic flows co-exist in complicated and chaotic ways: it can cause a lot of instabilities and put undesirable sheer forces on the aircraft, so the aerodynamic design of the aircraft is going to have a significant effect. Between the increased drag force associated with transonic speeds, the instabilities causing control problems, and possibly having to endure several shock waves, I speculate that it would take a lot more energy than traveling at either supersonic or subsonic speeds.