The length of copper rod at 50°C is 80 m and 100 m at 200°C. Find the linear expansivity.
A - 1.11 × 10⁻⁵ °C⁻¹
B - 1.44 × 10⁻⁵ °C⁻¹
C - 1.86 × 10⁻⁵ °C⁻¹
D - 2.25 × 10⁻⁵ °C⁻¹