Working alone at its own constant rate, a machine seals k cartons in 8 hours, and working alone at its own constant rate, a second machine seals k cartons in 4 hours. if the two machines, each working at its own constant rate and for the same period of time, together sealed a certain number of cartons, what percent of the cartons were sealed by the machine working at the faster rate? a. 25%b. $$ 33 \ frac {1} {3} \% $$c. 50%d. $$ 66 \ frac {2} {3} \% $$e. 75%