Steel train rails are laid in 12.0-m-long segments placed end to end. The rails are laid on

Question:

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 - 2.0°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°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°C?