In a certain application four inputs A, B, C, D are fed to logic circuit, producing an output which operates are lay. The relay turns on when ƒ(A, B, C, D) = 1 for the following states of the inputs (A B C D): 0000, 0010, 0101, 0110, 1101 and 1110. States 1000 and 1001 do not occur, and for the remaining states the relay is off. The minimized Boolean expression f is