Answer:
C = 1256.63 miles
Step-by-step explanation:
This problem is solved by using the following formula for the relation between the arc length of a circle and its radius:

s: arc length
r: radius
In this case "s" is 600 miles, and the angle of the arc length is 3°. With this information you can calculate the radius of the planet X:

With the value of the radius of the planet you can calculate the circumference, by using the following formula:
