I am currently using Richard Hamming's art of probability book to brush some basic concepts regarding the subject.
In this book, problem 1.7-17:
On the roll of two dice, what is probability at least one face having 4 or else the sum of the faces equals 4?
I am arriving at an answer of $7/18$ $(11/36 + 3/36 = 7/18).$
However , he mentions the answer to be $1/18.$
Is this an error or am I making a mistake in my calculation?