time and work problem A man can begin a work at his maximum rate; but afterwards the rate at which he works follows a cyclic pattern. Every 2 hr,it reduces by half but after 8 hrs,it comes back to its maximum level.He can complete a job in 151 Hrs at his maximum rate.How many hours would he take to complete the job if his rate follows the cyclic pattern?

Options are:

A. 301
B. 601
C. 641
D. 321

i am unable to understand this question.

Please help
The pattern is the following : 


0h $\rightarrow$ 2h : Work rate = 100% efficiency
2h $\rightarrow$ 4h : Work rate = 50% efficiency
4h $\rightarrow$ 6h : Work rate = 25% efficiency
6h $\rightarrow$ 8h : Work rate = 12.5% efficiency


And every time he reaches 8 hours of work, he gets back to 0h and works at 100% efficiency for 2 hours, etc.

The question is : if the worker was working at 100% every time, he would need 151 hours to get the job done. However he doesn't work at 100% every time, so you have to use the cycle to determine how long it would take.
$a= \text{maximum efficiency}$
$$X\times \frac{(a+\frac{a}{2}+\frac{a}{4}+\frac{a}{8})}{4} = a\times 151$$ solving for $x$ we get $$x=151\times \frac{32}{15} =321$$
$X$ gives us the effective working time