Gram_Stone comments on Open thread, Feb. 9 - Feb. 15, 2015

[Gram_Stone]

For the expression ~(A & B), B ∴ ~A, I came up with the following truth table, where a ‘+’ indicates a column of truth values for a premise:

A B ~ (A & B) , B ∴ ~A

T T F T T F F T T F T T T F T F F F F F T F F F

             +                         +

The solution in the book, however lists the conclusion in the fourth row is true rather than false:

A B ~ (A & B) , B ∴ ~A

T T F T T F F T T F T T T F T F F F F F T F F T

             +                         +

Have I made a mistake or is this an error?