Susan has just completed her second semester in college. She earned a grade of Upper A in her 3-hour topology course, a grade of Upper D in her 4-hour sociology course, a grade of Upper A in her 4-hour engineering course, and a grade of Upper A in her 5-hour philosophy course. Assuming that A equals 4 points, B equals 3 points, C equals 2 points, D equals 1 point, and F is worth no points, determine Susan's grade-point average for the semester.