Need Help With Sinusoidal Graphs

Hi all, I was sick and missed a day of pre-cal, and i missed an important lecture on sinusoidal graphs and word problems. I have a worksheet that has two problems, and I'm going to put the first one on so someone can help me and hopefully that will give me a jumpstart for doing the second. here it is:

*fox population problem*

Naturalists find that the populations of some kinds of predatory animal's vary periodically. Assume that the population T of foxes in a certain forest varies sinusoidally with time. Records started being kept when time t = 0 years. a minimum number, 200 foxes, occurred when t = 2.9 years. the next maximum, 800 foxes, occurred at t = 5.1 years.

1. sketch a graph of this sinusoid

2. write an equation expressing the number of foxes as a function of time, t.

3. predict the population when t = 7.

4. foxes are declared to be an endangered species when their population drops below 300. between what two nonnegative values of t were foxes first endangered?

5. show on your graph that your answers to part 4 are correct.

all help/tips appreciated