Additional Problem $5(15$ points$)$:

A round metal bar is supported on a piece of wood by a nut and washer fastened at the

end. The diameter of the bar is $23$ mm and the washer has an inner diameter of $26$ mm $.$

If a load P is applied to the bar that causes an axial normal stress of $36$ MPa in the bar,

determine the smallest outer diameter, d $,$ for the washer so that the average bearing

stress between the washer and wood does not exceed $6$ MPa $.$ Note: The entire washer

is in contact with wood.