Total power in an amplitude-modulated wave can be calculated using the formula:

Total Power = Carrier Power + Sideband Power

1. Calculate the Carrier Power:
The carrier power is given as 400 Watts.

2. Calculate the Sideband Power:
The modulation depth is given as 75 percent, which means the amplitude of the modulating signal is 0.75 times the amplitude of the carrier signal.
The sidebands in an AM wave carry the modulating signal and have an average power equal to half the power of the modulating signal.

Therefore, the sideband power can be calculated as follows:
Sideband Power = (0.5 * Modulating Signal Power) = (0.5 * Carrier Power * Modulation Depth^2)

In this case, since the modulating signal is sinusoidal, its power is proportional to the square of its amplitude.
So, the modulation depth squared is equal to the square of the amplitude of the modulating signal.

3. Calculate the Modulating Signal Power:
To calculate the modulating signal power, we need to know the peak amplitude of the modulating signal.

Let's assume the peak amplitude of the modulating signal is A. Then the power of the modulating signal can be calculated as:
Modulating Signal Power = (A^2) / 2

Since the modulation depth is given as 75 percent, the amplitude of the modulating signal is 0.75 times the amplitude of the carrier signal.
So, the peak amplitude of the modulating signal is 0.75A.

Plugging in this value, the Modulating Signal Power can be calculated as:
Modulating Signal Power = ((0.75A)^2) / 2 = (0.5625A^2) / 2 = (0.28125A^2)

4. Calculate the Sideband Power:
Using the formula for Sideband Power mentioned earlier:
Sideband Power = (0.5 * Carrier Power * Modulation Depth^2)
Substituting the values:
Sideband Power = (0.5 * 400 * (0.75^2)) = 0.5 * 400 * 0.5625 = 112.5 Watts

5. Calculate the Total Power:
Total Power = Carrier Power + Sideband Power
Total Power = 400 + 112.5 = 512.5 Watts

Therefore, the correct answer is option D) 512.5 Watts.