Need Help with Trig Modeling

Could someone help me with trig modeling problem?

4)Assume that are aboard a submarine, submerged in the Pacific Ocean. At time t=0 you make contact with an enemy destroyer. Immediately, you start "porpoising" ( going deeper and shallower). At time t= 4 minutes, you are at your deepest, y= -1000 meters. At time t= 9 minutes, you next reach your shallowest, y= -200 meters. Assume that y vries sinusoidally with t for t > 0.

a) Sketch the graph of y versus t.

b) Write the particular equation expressing y in terms of t.

c) Your submarine is "safe" when it is below y = -300 meters. At time t=0, was your submarine safee? Justify your answer.

Need help with Trig Modeling

Thanks Grandad! I already solved it! The ans I got is:

y = -400 sin (.628t -.943) - 600.