can anybody help me with this homework please?

1. A clock is logic 0 for 20ns and logic 1 for 50ns. a) ( 2 points) what is the period T? b) (2 points) what is frequency f? c) (2 points). what is the duty cycle? 2. (3 points) briefly explain the difference between a combinational and a sequential digital circuit. 3. (3 points) briefly explain the difference between a level-triggered device and an edgetriggered device. 4. (3 points) For latch circuits, briefly describe the significance of a setup time and a hold time