Harry Potter is at Ollivanders Wand Shop. As we all know, the wand must choose the wizard, so Harry cannot make the choice himself. He interprets the wand selection as a random process so he can determine the probabilities of different outcomes.

The wood types available are holly, elm, maple, and wenge. The core materials on offer are phoenix feather, unicorn hair, dragon scale, raven feather, and thestral tail.

Let

AA

A

A

be the event that Harry is chosen by a wand made of holly and

BB

B

B

be the event that he is chosen by a wand with a dragon scale core.

What is

P(A or B)P(A\text{ or }B)

P(A or B)

P, left parenthesis, A, start text, space, o, r, space, end text, B, right parenthesis

, the probability that Harry is chosen by a wand made of holly or a wand with a dragon scale core?