Consider a sequence of numbers $${a_1},{a_2},{a_3},....,{a_n}$$ where $${a_n} = {1 \over n} - {1 \over {n + 2}}$$, for each integer n > 0. What is the sum of the first 50 terms?

Each of the letters arranged as below represents a unique integer from 1 to 9. The letters are positioned in the figure such that (A $$ \times $$ B $$ \times $$ C), (B $$ \times $$ G $$ \times $$ E) and (D $$ \times $$ E $$ \times $$ F) are equal. Which integer among the following choices cannot be represented by the letters A, B, C, D, E, F or G?