The diagram shows an electric pump for a garden fountain that is linked to a $230\,\text{V}$ mains electrical supply by an $18\,\text{m}$ cable. The pump is considered to be performing acceptably when the potential difference (p.d.) across it is at least $218\,\text{V}$. At that point, the current through it is $0.83\,\text{A}$. What is the greatest resistance per metre of each of the two wires in the cable if the pump is to perform acceptably?
- A$0.40\,\Omega\,\text{m}^{-1}$
- B$0.80\,\Omega\,\text{m}^{-1}$
- C$1.3\,\Omega\,\text{m}^{-1}$
- D$1.4\,\Omega\,\text{m}^{-1}$