If Midge Can Address 100 Letters in an Hour, Frankie

If Midge can address 100 letters in an hour, Frankie can address 110 letters in an hour, and Tom can address 140 letters in an hour, then which of the following could represent the potential group productivity of the three working together as a group?

A) 350 letters per hour.
B) 315 letters per hour.
C) 140 letters per hour.
D) 100 letters per hour.