An electric kettle has two heating coils. When one coil is used, water in the kettle boils in $5$ minutes, while when second coil is used, same water boils in $10\,\min$. If the two coils, connected in parallel are used simultaneously, the same water will boil in time
  • A$3$ $\min$ $20$ $sec$
  • B$5$ $\min$
  • C$7\, \min$ $30\, sec$
  • D$2\, \min$ $30\, sec$
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