题目

The new high-speed railway line between Urumqi, capital of the Xinjiang Uygur self-governing region, and Lanzhou, capital of Gansu province, has cut train travel time by half to less than 12 hours.     The dramatic improvement will benefit many families planning reunions for Spring Festival.     For the first time, I feel home is not that far away after all, said Liang Shaofu as he boarded a high-speed train in Urumqi with six members of his family.     The 35-year-old left Lanzhou to set up a dry fruit business in Xinjiang eight years ago, and he has now settled in Urumqi.    已知且，则实数k=________．