What is the rate of depreciation

I have two questions about rate of depreciation? I don't understand how this works... Here are my questions.

A boat is worth $10,000 when it is 5 years old and $4,000 when it is 8 years old. What is the rate of depreciation?

a) $2,000

b)$2,500

c) $1,000

d) $1,500

A boat is worth $7,000 when it is 5 years old and $2,000 when it is 10 years old. What is the point slope equation?

a) y – 5,000 = 1,000(x – 2,000)

b) y – 7,000 = -1,000(x – 5)

c) y – 5 = 1,000(x – 7,000)

d) y – 2,000 = 1,000(x – 10)

1) Total depreciation is 10000-4000=6000, in 3 years. So depreciation is 2000 a year, a).

2)
7000=m*5 +c
2000=m*10 +c
so
m=(2000-7000)/5=-1000
c=12000
and
y=-1000x+12000, or

y-7000=-1000(x-5), answer b)