Find the thickness (mm) of a tube of internal diameter 100 mm if the internal pressure is 5/8 of the maximum permissible circumferential stress; find the increase in diameter (mm) when the internal pressure is 90 N/mm^{2} (E = 205 kN/mm^{2}, ν = 0.29, neglect longitudinal strain). Treat the tube as a thick cylinder (Lamé); the diameter is the internal diameter.