Steel train rails are laid in 12.0-m-long segments placed end to end. The rails are laid on a winter day when their temperature is -9.0$^\circ$C. (a) How much space must be left between adjacent rails if they are just to touch on a summer day when their temperature is 33.0$^\circ$C? (b) If the rails are originally laid in contact, what is the stress in them on a summer day when their temperature is 33.0$^\circ$C?