design a 4-bit counter F( represented by F3,F2,F1,F0) which can count the specified sequence as following: 0000->1000->1111->0110->0000. The counter will use the falling edge of the clock (denoted by Clk) and have a separte reset pin (R) which will reset the counnter to 0000 when it is low (e.g. R=0). Please use D type flip-flops. write down the state diagram , and state table ; use K- map to simpify the input equations; Write down the simplified input equations and draw a neat circuit diagram.