For the time question, what you're supposed to do is to use a sine function, makes it a hell of a lot easier.
Period = given time * 2
W = 2pi/period
then use 0.6 = 2.3 sin wt
find t
multiply t by 2
then subtract the answer from the given time.
Btw, I forgot to multiply the period by 2, how many marks would I lose?