pls help

Question:
A particular type of component for televisions is manufactured at three different factories A,B andC. Of the televisions produced by a certain company, 40% had the component manufactured at A,35% had the component manufactured at B and 25% had the component manufactured at C. Of the components manufactured at A, 1% are defective; the corresponding components manufactured at B and C are 2% and 4%, respectively.
a) Show that the probability of the component in a randomly chosen television produced by the company being defective is 0.021.

I've done parts b and c of this question but for reason i really can't seem to figure out a??