The best possible Answer is c
If it takes 42 minutes to load 3 1/2 trucks, then it takes 42 / 3.5 = 12 minutes to load a single truck. Multiplying the number of minutes per truck by 6.5 yields the time it will take to load. In this case 12 x 6.5 = 78 minutes would be required to load 6 1/2 trucks. The formula for the time taken is t = 12n, where t is the time in minutes and n is the number of trucks.
In order to have a period that matches the Earth's rotation, a satellite must be in a circular orbit, and 42,164 km from the center of the Earth.
But that's not quite enough to make sure that it always stays over the same point on the Earth's surface (and appears motionless in the sky). For that to happen, the satellite's orbit has to be directly over the Equator.
The Moon has nothing to do with any of this.
