On a straight railway track, absolute levels at point A on two rails are 100.550 m and 100.530 m and the absolute levels at point B 100 m apart are 100.585 m and 100.515 m respectively, the value of twist of rails per metre run, is

• 0.4 mm
• 0.5 mm
• 0.7 mm
• 0.8 mm
• 1.0 mm