الرجاء me 216

الرجاء حل هذين السؤالين ولكم مني خالص التحية والشكر
السؤال الأول

A polycrystalline brass specimen having an average grain diameter of 0.05 mm is heated to 600 oC at which grain growth is allowed to occur. If after 100 minutes the average grain diameter was noted to be 0.1 mm, determine how long it will take for the average grain diameter to reach 0.2 mm at the same temperature.​

السؤال الثاني
A metallic alloy with an average grain diameter of 0.003 mm and yield strength of 500 MPa was subjected to an annealing process and grain growth was allowed. As a result the alloy suffered an increase in grain diameter from 0.003 mm to 0.009 mm and its yield strength was reduced to 320 MPa. If the material was subjected to a sequence of cold working and annealing processes resulting in a final grain diameter of 0.001 mm, then calculate the final yield strength of the alloy.