To develop this problem it is necessary to apply the concepts related to the kinematic equations of motion. And from the speed found the relationships between wavelength, frequency and last of the period (which is inversely proportional to the frequency)
PART A) We know that the velocity of a body or a wave is equivalent to the distance traveled over a time interval. So,
Where
x = Distance
t = time
PART B) The frequency would then be defined as
Where
PART C) Finally the period is defined as