Explanation

Train A leaves at 7 p.m. at 60 km/h, so by 4 a.m. it has covered 9 × 60 = 540 km of the 800 km. The remaining 260 km closes at 60 + 90 = 150 km/h, taking 260/150 = 26/15 h. In that time B covers 90 × 26/15 = 156 km from Q, option (c).