I just wanted to know if I'm in the right direction because, well, statistics class hates me!

"The owner of a Auto-Parts Store has four employees (K, L, M, N) that make make mistakes in the preparation of a Sales Order in the following ratio: 1 to 20; 1 to 10; 1 to 10 and 1 to 20, respectively. Of all the orders prepared by K, L, M, N they are 20%; 60%; 15% and 5%, respectively. If an error occurs in an order, what are the probabilities that they were prepared by K, L, M, N?"

For "K", there's a 1 out of 20 chance that he made the mistake. That's a 5%. Times that by the percent of all sales orders they do (20%) and you get there's a (1%) chance that he made the mistake................ right?

Thank you!