(I)
firstly , we will find maximum and minimum y-value
we can see that
maximum value is 5
minimum value is -5
so, we can find amplitude

..........Answer
(II)
we know that
wave length is the length of one wave
we can see that from B to F , there is one wave
and we are given it's length as 20cm
so, wavelength is 20cm......Answer
(III)
we know that

we are given
frequency =100hz
wavelength =20cm
now, we can find velocity

............Answer