Let's calculate No of Units as Revenue / Unit price. Per Unit cost as (Revenue - Profit ) / No of Units. In that way, we calculate the table as follows.
YEAR
UNIT PRICE
REVENUE
PROFIT
NO OF UNITS
PER UNIT COST
2000
10
700
0
70
10
2001
14
1400
100
100
13
2002
12
1200
300
100
9
2003
12
900
150
75
10
2004
11
1100
0
100
11
2005
8
400
150
50
5
2006
10
200
100
20
5
2007
14
700
200
50
10
2008
10
600
0
60
10
2009
10
800
400
80
5
2010
15
900
300
60
10
It is clear from the table per unit cost in the year 2001 is the highest. Hence B is the correct answer.1