You should calculate like this: 595/5= $119
1st set = 4 letters
2nd set = 4x 4 = 16 letters
3rd set = 16 x 4 = 64 letters
4th set = 64 x 4 = 256 letters
5th set = 256 x 4 = 1,024 letters
6th set =1024 x 4 = 4,096 letters
7th set = 4096 x 4 = 16,384 letters
8th set = 16,384 x 4 = 65,536 letters
Each letter cost 2
Total cost = 65,536 x 2 = 131,072
C) 5s - 0.2s is not equivalent. This would be paying for 5 snakes and subtracting 20% of the price of one snake, not 20% of the price of all 5 snakes.
When you arrange the N points in sequence around the polygon (clockwise or counterclockwise), the area is half the magnitude of the sum of the determinants of the points taken pairwise. The N determinants will also include the one involving the last point and the first one.
For example, consider the vertices of a triangle: (1,1), (2,3), (3,-1). Its area can be computed as
(1/2)*|(1*3-1*2) +(2*-1-3*3) +(3*1-(-1)*1)|
= (1/2)*|1 -11 +4| = 3