guerrero wrote:Three copy machines are making copies of the same document. Copier A makes 12 copies per minute, Copier B makes 7, and Copier C makes 19. It costs 8 cents/copy for Copier A, 5 cents/copy for Copier B, and 11 cents/copy for Copier C. If a separate attendant has to be hired for each copier and be paid $30 per hour (you have to pay $60 if the attendant works for one hour and one minute), which copier alone will be the most efficient choice to make 1,200 copies?

A)Copier A
b)Copier B
c)Copier C
d)A and B
e)A and C

OAB

Machine A:
Time = pages/rate = 1200/12 = 100 minutes.
Since the time is between 1 and 2 hours, the worker is paid for 2 hours.
Worker cost = (hourly wage)(number of hours) = r*t = 30*2 = $60.
Page cost = (cents per page)(number of pages) = 8*1200 = 9600 cents = $96.
Total cost = 60+96 = $156.

Machine B:
Time = pages/rate = 1200/7 ≈ 170 minutes.
Since the time is between 2 and 3 hours, the worker is paid for 3 hours.
Worker cost = (hourly wage)(number of hours) = r*t = 30*3 = $90.
Page cost = (cents per page)(number of pages) = 5*1200 = 6000 cents = $60.
Total cost = 90+60 = $150.
Since B is a better option than A, eliminate A.

Machine C:
Time = pages/rate = 1200/19 ≈ 60+ minutes.
Since the time is between 1 and 2 hours, the worker is paid for 2 hours.
Since A's time is also 2 hours, and A's page cost is LESS than C's, A is a better option than C.
Thus, B is better than A, and A is better than C, B is better than C.
Eliminate C.

Machines A and B together:
Since their combined rate = 7+12 = 19 pages per minute, the time will be the same as C's time (2 hours).
Cost for 2 attendants working for 2 hours each = (number of workers)(hourly rate)(number of hours) = 2*30*2 = $120.
Since B's page cost for the entire job = $60, and A's page cost is GREATER than B's, the total cost for A and B together must be MORE than 120+60 = $180.
Thus, B alone is a better option.
Eliminate D.

Machines A and C together:
Since their combined rate = 7+19 = 26 pages per minute, the time for A and C together = pages/(combined rate) = 1200/26 = less than 60 minutes.
Since the time is less than 1 hour, the 2 workers are paid for 1 hour each.
Cost for 2 attendants working for 1 hour each = (number of workers)(hourly rate)(number of hours) = 2*30*1 = $60.
Since A's page cost for the entire job = $96, and C's page cost is GREATER than A's, the total cost for A and C together must be MORE than 60+96 = $156.
Thus, B alone is a better option.
Eliminate E.

The correct answer is B.