What is the measure of arc adb? what is the length of arc adb? what is the area of the shaded region?

What is the measure of arc ADB?
 The measure of the arc for this case is given by the following angle:
 theta = 360-90
 theta = 270 degrees

 What is the length of arc ADB? 

 The arc length is given by:
 s = R * theta
 Substituting values:
 s = 15 * (270 * (pi / 180))
 s = 70.69 m

 What is the area of the shaded region?

 The area of the shaded region is:
 A = (s' / s) * (pi) * (r ^ 2)
 Substituting values:
 A = (270/360) * (3.14) * (15 ^ 2)
 A = 529,875 m ^ 2

The linear equation is: y=ax+b