In A(¯¯¯a),B(¯¯b),C(¯¯c),D(¯¯¯d) are two vertices of trapezium .E(¯¯¯e),F(¯¯¯f) are midpoints of sides AD and BC, then
A(0, 0), B(6, 0), C(4, 2), D(2, 2) are the vertices of trapezium ABCD.
E and F are the midpoints of AD and BC respectively then, EF =?.