Factory overhead costs for a given period were 3 times as much as the direct material costs. Prime costs totaled $2,100. Conversion costs totaled $3,400. What are the direct labor costs for the period?

I tried looking for help on this problem and I think I may need to do a "substitution method" but I am still confused on how to do it and get the correct answer. If you could take the time out of your day to explain each step/why you're preforming the step that would be great (: Thank you.

a) 1500

b) 1450

c) 1630

d) 1310