In a parallel-flow, water-to-water heat exchanger, the hot water enters at 75°C at a rate of 1.2 kg/s and cold water enters at 20°C at a rate of 0 9 kg/s. The overall heat transfer coefficient and the surface area for this heat exchanger are 750 W/m² · K and 6.4 m², respectively. The specific heat for both the hot and cold fluid may be taken to be 4.18 kJ/kg · K. For the same overall heat transfer coefficient and the surface area, the increase in the effectiveness of this heat exchanger if counter-flow arrangement is used is
(a) 0.09

(b) 0.11

(c) 0.14

(d) 0.17

(e) 0.19