Working alone at a constant rate, Alan can paint a house in a hours. Working alone at a constant rate, Bob can point 1/4 of the same house in b hours. Working together, Alan and Bob can paint 1/3 of the house in c hours. What is the value of b in terms of a and c?	Select:
A) (3ac)/(a+c)
B) (4a-12c)/(3ac)
C) (3ac)/(4a-12c)
D) (ac)/(a+2c)
E) (ac)/(a+c)
work time   A 1 a   B 1/4 b   A+B 1/3 c   A's rate = 1/a   B's rate = 1/4b   when they are working together , their combined rate is 1/a + 1/(4b) = (1/3)/c   1/(4b) = 1/(3c) - 1/a   =&gt; b = 3ac /(4a-12c)   Answer is (3ac)/(4a-12c).
<result>C</result>
Working alone at a constant rate, Alan can paint a house in a hours. Working alone at a constant rate, Bob can point 1/4 of the same house in b hours. Working together, Alan and Bob can paint 1/3 of the house in c hours. What is the value of b in terms of a and c?