text: ﻿function inputLine(form) {
      var a = form.a.value;
      var b = form.b.value;
      var h = parseFloat(form.h.value);
      var trapezoidArea;
      if (!isNaN(a) && a !== '' &&
          !isNaN(b) && b !== '' &&
          !isNaN(h) && h !== '' &&
          a > 0 && b > 0 && h > 0) {    
              trapezoidArea = (((a * 1) + (b * 1)) * (h * 1)) / 2;
              alert("The trapezoid area is: " + trapezoidArea);             
      }
      else {
          alert("Not valid numbers for a,b and h. Try again.")
      }
  }