Could it ever be clearer enough? I passed there the other day and noticed that in lieu of GHC20.00, should you dare challenge the message on the wall, you'll be charged GHC50.00!
Unless the originators of the message have mounted invisible cameras, or have deployed a standing force comparable to Gil Grissom of CSI-Las Vegas fame to take your urine sample for "trace" analysis, in order to determine who micturated, I am not quite sure how it will be enforced!
Students of CSI Tamale, take note!:-)