. Find the angle between the straight line connecting (1, 3, -2) and (2,5,-1) and the straight line connecting (-1, 4,3) and (3,2, 1).

2.ABCD is the base of a quadrangular pyramid with a side length of 2 units, and V is the vertex. The pyramid is symmetrical, with a height of 4 units. Calculate the acute angle between AV and BC, and give the answer accurate to 1 after the decimal point.