Which of the following setups, when solved, would give you the number of seconds in one week?

a) 1 week x 7 days/1 week x 24hr/1 day x 60s/1hr =

b) 1 second x 1min/60s x 1hr/60min x 1 day/24hr x 1 week/ 7 days =

c) 1 week x 7 days/1 week x 24hr/1 day x 60min/1hr x 60s/1min =

d) 1 week x 1 week/7 days x 1 day/24hr x 1hr/60 min x 1min/60s =

Please please help. It's a question about conversion factors