Answer:
Twice.
Step-by-step explanation:
If a soil with 3% moisture has twice the rate of erosion as compared to the soil having 7% moisture if both experience same speed of wind i. e. 15 m/s. This is because moisture held the particles of soil tightly with each other and prevent erosion in the soil so if the moisture becomes half in the soil then the rate of erosion is twice or doubled at constant wind speed.