a threaded steel rod es = 210 gpa dr = 15 mm as = 12 * 10^negative 6/ degree Celsius is held stress free between rigid walls by a not and a washer dw = 22 mm assembly at each end if the allowable bearing stress between the washer and wall is 55 mpa and allowable normal stress in the rod is 90 mpa calculate the maximum permissible temperature drop