During a tensile test of a round metal specimen with an initial diameter of 12.8 mm, a maximum load of 53.4 kN is reached. At this load the...

During a tensile test of a round metal specimen with an initial diameter of 

12.8 mm, a maximum load of 53.4 kN is reached. At this load the cross-sectional 

area is 60% of the starting initial area. Calculate the mean true flow stress of the 

metal during this deformation.