By how much did the price of one gram of gold change from the beginning of week 1 to the end of the week 4? did the price increase or decrease?

The complete question in the attached figure

we know that
Part a):
From the table,
iweek 1, the price increased by $1.25,
iweek 2, the price decreased by $3.125,
week 3, the price increased by $0.625
week 4, the price increased by $1.5
After the 4 week the change in price is given by
1.25 - 3.125 + 0.625 + 1.5 = 0.25.
Therefore

the answer Part a) is
the price changed over the 4 weeks period by $0.25.

Part b):
After the 4 week the change in price is given by
1.25 - 3.125 + 0.625 + 1.5 = 0.25
0.25  > 0
Therefore, 

the answer part B) isthe price increased over the 4 weeks period.

Part c)Given that the price of 1 gram of gold was $39.28 at the end of week 4.
and
 the price of 1 gram of gold increased by $0.25 over the 4 weeks period,
thus
 the price of 1 gram of gold at the beginning of week 1 is given by:
39.28 - 0.25 = $39.03

the answer Part C) is
the price of 1 gram of gold at the beginning of week 1 is $39.03

In all honesty, there really is no “work” per say to show. mainly it’s just using the process of elimination. the question is asking which domain(s) would be the most appropriate for the function c(n). n is the number of observed vehicles so right away, 1, 2, and 3 can be eliminated.why? 1, 2 start in the negatives and therefore it is impossible to observe negative cars. so, #4 would be the best answer to the given problem.