Consider a parallel-flow heat exchanger with area Ap and a counter-flow heat exchanger with area Ac. In both the heat exchangers, the hot stream flowing at 1 kg/s cools from 800C to 500C. For the cold stream in both the heat exchangers, the flow rate and the inlet temperature re 2 kg/s and 100C, respectively. The hot and cold streams in both the heat exchangers are of the same fluid. Also, both the heat exchangers have the same overall heat transfer coefficient. The ratio $A_{c}/A_{p}$ is _______