Calculate the sum of the following mixed fractions.  $$1\frac{1}{3}+2\frac{9}{12}+3\frac{3}{5}+4\frac{1}{4}+5\frac{4}{6}+6\frac{10}{25}$$ 
选项为:A:$$18$$  B:$$19$$  C:$$21\frac{7}{12}$$  D:$$24$$  E:None of the above  请回答其中一个选项.