Can someone please explain the steps to solving the problem below?

Consider a multi-level computer interpreting all levels where: all Level 1 instructions are converted to 8 Level 0 instructions; all Level 2 instructions are converted to 8 Level 1 instructions all Level 3 instructions are converted to 3 Level 2 instructions; all Level 4 instructions are converted to 8 Level 3 instructions all Level 5 instructions are converted to 8 Level 4 instructions; all Level 1 instructions are 7 as powerful' as Level 0 instructions; all Level 2 instructions are 9 as 'powerful' as Level 1 instructions; all Level 3 instructions are 5 as powerful' as Level 2 instructions; all Level 4 instructions are 6 as powerful' as Level 3 instructions; and all Level 5 instructions are 8 as 'powerful as Level 4 instructions. If a Level 0 instruction takes 15.9 ns to execute a task, how many ns does it take to execute an equivalent task on Level 4? (Give your answer to one decimal place.)