Design the simplest circuit that has four inputs, a, b, c, and d, which produces an output value of 1 whenever three or more of the input variables have the value 1; otherwise, the output has to be 0. You can only use AND gates and OR gates with any number of inputs and NOT gates. Let the cost of a logic circuit be the total number of gates plus the total number of inputs to all gates in the circuit. What is the cost of your circuit?