Using Addition Rule 2:

A cell phone company gets a really good deal on 400 Samsung phones. Of them, 250 have 5" screens and the rest have 4" screens, Of the phones with 5" screens, 140 are silver and the rest are black. Of the phones with 4" screens, 80 are silver and the rest are black. If one phone is picked at random for a customer, find the probability that it will: (B) Be black or have a 4" screen.