Machines X and Y produce bottles at their respective constant rates. Machine X produces k bottles in 3 hours and machine Y produces k bottles in 2 hours. How many hours does it take machines X and Y , working simultaneously , to produce 12k bottles?	Choose one:
A) 16	B) 20	C) 15	D) 72/5	E) 24
x rate = k/3   y rate = k/2   k/3 + k/2 = 12k / T   solving T = 72/5   Answer 72/5
<result>D</result>
Machines X and Y produce bottles at their respective constant rates. Machine X produces k bottles in 3 hours and machine Y produces k bottles in 2 hours. How many hours does it take machines X and Y , working simultaneously , to produce 12k bottles?