A road network (shown in the figure below) connects cities A, B, C and D. All road segments are straight lines. D is the midpoint on the road connecting A and C. Roads AB and AC are at right angles to each other with BC shorter than AB. The segment AB is 100 km long.
Mr. X and Mr. Y leave A at 08:00 am, take different routes to city C and reach at the same time. X takes the highway from A to B to C and travels at an average speed of 61.875 km per hour. Y takes the direct route AC and travels at 45 km per hour on segment AD. Y’s speed on segment DC is 55 km per hour.
When $10^{100}$ is divided by 7, the remainder is ?