!Increase loop
   FOR x=0 to 21 step .001
       LET a=(h-z)/(w^2)
       LET b=a*((x-w)^2)+z
       !Tests inside loop to see if conditions are good to go.
       IF (x>=18 and x<=19) and b=12 then
          PRINT "Hooray! You're Fantastic!"
          LET n$="pie'rat"
       END IF
       PLOT x+3,b
   NEXT x
   !If failure, reprompt.
   IF n$<>"pie'rat" then
      PRINT "Try again if you please."
   END IF