Shell gas station is having a sale on diesel. If you buy 3 gallons or less, you pay the regular price of $2.29 per gallon. If you buy more than 3 gallons, you pay $1.99 per gallon. Write a piecewise function for the price of n\displaystyle {n} gallons of diesel at Shell.

D(n)={\displaystyle {D}{\left({n}\right)}={\left\lbrace\begin{array}{c} \\\\\end{array}\right.}   if 0<n\displaystyle {0}<{n}\le
  if n>\displaystyle {n}>