Answer
a) no change
b) half
Work Step by Step
(a) We know that the wave speed in a medium depends on the properties of the medium. Since the tension and mass per length are constant, the wave speed is unchanged (or in other words, multiplied by a factor of 1.0).
(b) We know that $v=\lambda f$. We are given that the speed is constant, so the wavelength becomes half by doubling the frequency (or in other words, it is multiplied by a factor of 0.5).
