So angle center of gravity = angle fog

Because angle AOC: Angle AOC=4:7.

So AOC: COF=4: 14.

Because EF is perpendicular to AB

So AOF angle =90 degrees BOF angle.

So angle AOC+ angle COF = 90° divided by (14+4).

So the angle AOC=5 degrees

Because angle AOC= angle DOB (relative vertex angle)

So the angle DOB=5 degrees

Because angle DOF= angle DOB+ angle BOF

Because DOB=5 and BOF=90.

So the angle DOF = 95