Need help with trig graph questions

Hi, there are a few trig questions I'm not sure how to work out:

The equation y = a cos bx can be used to describe some natural cycles, such as tides and the phases of the moon.

1] Determine the constants a and b and write the equation representing the scenario.

a) A 12 hour gap between high tides of 2.3m and low tides of -2.3m

b) Same as a), except tides vary from 0.7m to 5.3m.

2] State the greatest possible value of 2sin(x - 30 deg) and the smallest possible value of x that will get this maximum value.

3] State the period, amplitude and range of this equation: y = -2sin(x - 45 deg) + 2

Thanks in advance for help, and please explain your working. Thanks!