A solution of density 1100 kg/m3 and heat capacity 4.6 kj/kgK is heated from 65°C to 100°C by steam condensing at 115°C. The flow rate of the solution is 11.8 kg/sec. Solution flow in tubes of diameter 25 mm at 1.2 m/s Length of the tube is not to exceed 3.5 m Taking inside and outside heat transfer coefficient as 5 and 10 Kw/m2k respectively Find the sum of the number of tubes and number of passes per tube.