5x 15
This is the answer to your question
Need more info: which one is the height? which is the lenght and which is width? and what type of prism is it?
"60 is..." can be translated with 
"5 times as great as k [/tex] means 
So, the equation is

To solve for k, divide both sides by 5:

Which leads to

7.998/0.7008=11.41267123287671
That's a big answer haha...
Well I hope this helps! :D