Interrupts and bus arbitration require means for selecting one of several requests based on their priority. Design a circuit that implements a rotating-priority scheme for four input lines, REQ1 through REQ4. Initially, REQ1 has the highest and REQ4 the lowest priority. After some line receives service, it becomes the lowest priority line, and the next line receives highest priority. For example, after REQ2 has been serviced, the priority order, starting with the highest, becomes REQ3, REQ4, REQ1, REQ2. Your circuit should generate four output grant signals, GR1 through GR4, one for each input request line. One of these outputs should be asserted when a pulse is received on a line called DECIDE.