Geometry

Question Analysis:
This problem applies the exterior angle sum property to an irregular pentagon.

Key Concept Explanation:
The exterior angle sum for any pentagon is 360°.
Unlike regular polygons, irregular polygons have varying exterior angles.

Step-by-Step Solution:
Sum of given angles: 70° + 80° + 90° + 60° = 300°
Subtract from total sum: 360° - 300° = 60°

Common Mistakes:
Using interior angle sum formula (540° for pentagon) incorrectly.
Arithmetic errors in summing the given angles....