Sir,
In Q9, there is not mentioned to approximate the answer and clearly mentioned that answer should be with in accuracy upto 4 decimals ,,,so why are you not considering 0.1888 as answer.
And also In practice assignment of week 2 ,In Q7 and Q8 you have fixed the range from accurate answer to approximation...
So here in graded assignment , there should be the fixed range for answer...
Kindly look through this issue..