What are the speeds for absolute ceiling and coffin corner?
At absolute ceiling we can fly at only one speed. This is the speed
  which corresponds to intersection of power available and power
  required curves?


The "intersection of power available and power required" is anywhere along the left hand edge of the red cross-hatched area. The absolute ceiling is the intersection of the stall curve (left-most red line) with this power limit.


  And what is that speed at which flight at Coffin Corner is only possible?


Coffin corner in that chart should be the intersection of the red stall line with the black MMO/VMO line. 

I say 'should be' because the stall line is drawn with a maximum at the  "absolute aerodynamic ceiling" i.e. the plane stalls if it goes any faster or slower. Stalling when going faster must be due to increased Mach number.

In other words, the right hand side of the stall line is actually the maximum Mach number, which would make the "absolute aerodynamic ceiling" 'coffin corner'.

I suspect the confusion is that they wanted to draw MMO as a (mostly) straight line, and didn't think it mattered because the plane doesn't have the power to reach that region.