An aluminum alloy with an initial, average grain diameter of π3.4 × 10⁻3π mm is heated in a furnace to π650⁰ Cπ for 30 minutes. The average grain diameter increased to π1.1 × 10⁻2π mm. Find
a) π8.2 × 10⁻3π mm
b) π7.7 × 10⁻3π mm
c) π6.3 × 10⁻3π mm
d) π5.9 × 10⁻3π mm