Answer
a) Constructive.
b) Destructive.
Work Step by Step
a) First of all, we need to find the wavelength of the television signal which is given by
$$v=\lambda f$$
Hence,
$$\lambda=\dfrac{v}{f}$$
Plugging the known;
$$\lambda=\dfrac{3\times 10^8}{75\times 10^6}=\bf 4\;\rm m$$
Now we know that the reflected signal is having180$^\circ$ a phase change. This means that when the signal reached from the station to the receiver with an integer number of wavelengths, then we got a constructive interference if the reflected signal is having an integer number of one-half wavelength, and vice versa.
Let's see the number of wavelengths to the receiver from the plane.
$$N=\dfrac{y}{\lambda}=\dfrac{122}{4}=\bf 30.5\;\rm wave$$
Therefore, we got $\bf constructive\; interference$ at the receiver.
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b) By the same approach as we did above, let's see the number of wavelengths to the receiver from the plane while the plane is 22 m (which means that it is above the receiver by 100 m).
$$N=\dfrac{y}{\lambda}=\dfrac{100}{4}=\bf 25\;\rm wave$$
Therefore, we got $\bf destructive\; interference$ at the receiver.
