4. If a is average number of peaks more than 10 mm of uneveness per kilometre, b is average number peaks more than 6 mm for gauge variation per kilometre and c is average number of peaks more than 2 mm twist per metre, then composite current recording index (Ic), as recommended by Indian Northern Railways, is
5. If D is the distance between parallel tracks G is the gauge and ? is angle of crossings, the distance between theoretical noses of two crossings measured parallel to tracks, is
8. If S is the switch angle and ? is diamond angle, r is the radius of slip, the distance between middle point slip and the nose of obtuse crossing, is