680. To measure distance on a Mercator chart between the parallels of LAT 34°30'N and LAT 31°30'N, which 30- mile scale should be used?

To minimize distortion when measuring north-south distance on a Mercator chart between latitudes 3430′N and 3130′N, use the 30-mile scale centered on the mid-latitude, which is 3245′N to 3315′N.