Draw a timing diagram with the following signals (where [t1, t2] is the time interval starting at t1 and ending at t2): a.signal A is stable [0,10], changing [10,15], stable [15,30] b.signal B is 1 [0,5], falling [5,7], 0 [7,20], changing [20,30] c.signal C is changing [0,10], 0 [10,15], rising [15,18], 1 [18, 25], changing [25, 30]