1. The problem states: "The answer a,b,c,d" which suggests we are dealing with multiple parts named a, b, c, and d. 2. However, no specific mathematical problem or values are provided to compute or analyze. 3. Please provide a clear algebraic, numeric, or conceptual question involving parts a, b, c, and d for solving or explaining. 4. Without more information, it isn't feasible to proceed with step-by-step solutions. 5. Once you share the details, I can guide you through each part with full explanation and calculations.