The length of an arc in a circle is radius x the angle (Ф).
Mind you angle Ф should be in radian. In our case we have the arc length & the radius, find the angle (Ф) Arc Length = Ф x 4 = 10 meters ===> Ф=10/4 =5/2 = 2.5 RADIANS
Now let's convert 2.5 RADIANS into DEGREE: 2.5/π = x/180 ===> x= (2.5 x 180) / π ==>143.239° or 143.24° (A)