Can I Have The Working How To Calculate It? Thanks a lot!

12. The table below shows the number of boxes of 100 tubes containing defectives: Firm Number of defective tubes 2 3 or more Supplier A 500 200 200 100 Supplier B 320 160 80 40 Supplier C 600 100 50 50 If one box had been selected randomly, what is the probability that (a) the box would have come from Supplier A? (b) it would have no defectives and come from Supplier A? (c) it would have no defectives or come from Supplier A