A machine produced $70$ pieces in two hours. However, two pieces were usuable. To produce $6800$ pieces with two machine

a$.$In one week $(5$ days$),$ how many hours a day should we run both machines?

b$.$how many business days $(8$ hours per day$)$ should we run this machine?

c$.$Which one do you prefer? Why?

d$.$If your customer requested the delivery in $8$ business days? What should you do$?$

e$.$If the max working hours for a machine is $10$ hours a day, what options you can propose your customer?