如图，请根据下列提示作图：

（1）先将△ABC向上平移2个单位长度，得到△A′B′C′；

（2）再将△A′B′C′向右移4个单位长度，得到△A″B″C″；

（3）若BC=3cm，∠BAC=70°，∠ABC=45°，则B′C′=______cm，∠B″C″A″=______°．

On the number line above, the segment from 0 to 1 has been divided into fifths, as indicated by the large tick marks, and also into sevenths, as indicated by the small tick marks. What is the least possible distance between any two of the tick marks