John can complete a given task in 20 days. Jane will take only 12 days to complete the same task. John and Jane set out to complete the task by beginning to work together. However, Jane was indisposed 4 days before the work got over. In how many days did the work get over from the time John and Jane started to work on it together? Select the correct option:
A) 6
B) 10
C) 8
D) 7.5
E) 3.5

Rationale: "john 6 * 20 = 120 jane 10 * 12 = 120 in 4 days working alone john did : 4 days * rate = 4 * 6 = 24 , so working together they did 120 - 24 = 96 - - > rate ( a + b ) * t = 96 - > 16 * t = 96 , t = 6 . hence the answer is b ( john worked 4 days + 6 days they worked together = 10 days )"
Answer: B