10. P(lat 400N, long 18°W) and Q(lat 400N, long 78OW) are two cities on the surface of the earth. Calculate, the: (a) the radius of the parallel of latitude on which P and Q lie, correct to the nearest 10km;
(b) length of the minor arc PQ, correct to the nearest 100 km;
(c) the vertical distance between the centre of the earth and the centre of the small circle on which P and Q lie, correct to the nearest km.
[Take π = 22/7 and radius of the earth= 6400 km]​