a_example - (Optimal: 21)
b_read_on - (Optimal: 5,822,900)
c_incunabula - (Optimal: 5,645,747)
d_tough_choices - (Optimal: 4,812,730)
e_so_many_books - (Optimal: 5,019,670)
f_libraries_of_the_world - (Optimal: 5,240,161)
Total - (Optimal: 26,541,229)