A company produces three models of video cassette$$ player, models$$ X$,$ Y$,$ and Z$.$ Each model X machine requires of electronics$$ work, $2\mathrm{.}8$ hours of assembly$$ time, and $4\mathrm{.}4$ hours of quality assurance time. Each model Y machine requires of electronics$$ work, of assembly$$ time, and of quality assurance time. Each model Z machine requires of electronics$$ work, of assembly$$ time, and of quality assurance time. There are available each week for$$ electronics, for$$ assembly, and for quality assurance. How many of each model should be produced each week if all available time must be$$ used?