Ten identical cells connected in series are needed to heat a wire of length one meter and radius...

Ten identical cells connected in series are needed to heat a wire of length one meter and radius \( r \) by \( 10^{\circ} \mathrm{C} \) in time \( t \) . How many cells will be required to heat the wire of length two meter of the same radius by the same temperature in time \( t \) ?
(a) 20
(b) 30
(c) 40
(d) 10