Velma and Shaggy are debating on which cleaning solution to use when cleaning the Mystery Machine based on how strong the solution may be.

Velma recommends using a 0.25 M NaOH solution with a pH of 13.40.
Shaggy recommends using a 0.025 M NaOH solution with a pH of 12.50.

Who is recommending the stronger cleaning solution, Velma or Shaggy? Why is their recommendation correct?