Ten percent of the pens made by Apex are defective. Only 5% of the pens made by

Question:

Ten percent of the pens made by Apex are defective. Only 5% of the pens made by its competitor, B-ink, are defective. Since Apex pens are cheaper than B-ink pens, an office orders 70% of its stock from Apex and 30% from B-ink. A pen is chosen at random and found to be defective. What is the probability that it was produced by Apex?
Use Bayes' theorem to calculate the probabilities?