5 men and 12 boys finish a piece of work in 4 days, 7 men and 6 boys do it in 5 days. The ratio between the efficiencies of a man and boy is? Choose the correct choice from the following:
A) 1:5  B) 6:5  C) 4:5  D) 9:5  E) 8:5
6:5   6:5   5M + 126:5 ----- 4 days   7M + 66:5 ------- 5 days   20M + 486:5 = 35M + 306:5   186:5 = 15M =&gt; 5M = 66:5   M: 6:5 = 6:5
<result>B</result>
5 men and 12 boys finish a piece of work in 4 days, 7 men and 6 boys do it in 5 days. The ratio between the efficiencies of a man and boy is?