A displacement–position graph of a transverse wave on a stretched string, taken at one instant, shows successive crests at x = 20 cm and x = 95 cm. The wave travels along the +x-direction with a speed of 25 m s⁻¹.
a. (i) Determine the wavelength.
b. (ii) Calculate the frequency.
c. (iii) Find the time period of the wave.