The breaking stress of a wire of length $L$ and radius $r$ is $5 \ kg-wt/m^2$. The wire of length $2L$ and radius $2r$ of the same material will have a breaking stress in $kg-wt/m^2$ of:

• A
  $5$
• B
  $10$
• C
  $20$
• D
  $80$