Tax allowable depreciation

Pls help me about this question:
In the study text, we have sample about Tax allowable depreciation
initial investment =300 depreciation on reducing balance, life =3 yrs.
Tax =50%.
The question about the answer is:
1. Why life time = 3 yrs, they calculate depreciation for 4 yrs
2. Why tax save on Tax allowable depreciation, say 18,750 is at year 0?

I am confused about it. I think it should be
1. only 3 yrs
2. at year 1

Pls help me!