∴∠AMD=90。
∫∠ABM = 45,
∴∠BAM=∠ABM=45,
∴AM=BM.
In Rt△ABM, from Pythagorean theorem, we get
AM=32。
∫∠D = 30,
∴AD=2AM,
∴AD=62.
Now the length of the advertisement on the slope is 62 meters.