1. The problem statement, all variables and given/known data 1. A nuclear power plant contains three danger sensors X, Y and Z that can shut down the plant. Sensor Z is in such a senstive location that it has a backup B. The plant is to be shut down if two of the three sensors indicate danger. However, with exception, sensor Z is the only registering danger sensor so that the plant to be shut down. Design the logic circuit of danger sensors. 2. Let A, B, C and D represent the binary digits of a decimal number in the range 0 to 15. Construct a simplified expression and draw the logic circuit diagram that will give a prime number checker. 2. Relevant equations Karnaugh map and truth table 3. The attempt at a solution 1. I have no idea how to incorporate the back-up and also what the third sentence means. Any clues, please? 2. I got Y = A'B'C + B'CD + A'BD + BC'D from the Karnaugh map. Is that the correct simplified expression?