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Definite integral basics challenge

Given:   k2kf(x)dx=2   ~~\displaystyle \int_k^{2k}f(x)\,dx=-2~~~ and    k5kf(x)dx=6~~~\displaystyle \int_k^{5k}f(x)\,dx=6\,,space, space where  k>0~k>0\,.
What is the value of   2k5kf(x)dx~~\displaystyle \int_{2k}^{5k}f(x)\,dx\,?