The purity of gold is measured in karats. Twenty-four karat gold is pure gold and k karat gold is k/24 gold by mass. One piece of 16-karat gld jewelry has a mass of 30 grams and another piece of 10-karat gold jewelry has a mass of 40 grams. Find the number of grams in the positive difference between the amount of pure gold in each piece of jewelry. Express answer as a mixed number.