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. \(75\%\)