Q26. A heater is designed to operate with a power of 1000 W in a 100 V line. It is connected in combination with a resistance of $10 \Omega$ and a resistance $R$, to a 100 V mains as shown in figure. For the heater to operate at 62.5 W ,\\
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the value of $R$ should be $\_\_\_\_$ $\Omega$.