In the figure a steel rod passes through a copper tube of the same length; rigid washers and nuts at both ends are just snug (no stress) at 20 °C. The whole assembly is heated uniformly to 100 °C. Using the dimensions and properties on the figure, determine (a) the stress in the steel rod (answer in MPa, state tension or compression), (b) the stress in the copper tube (answer in MPa, state tension or compression) and (c) the increase in length of the assembly (answer in mm).