The following table lists the age (rounded to the nearest year) and price (rounded to the nearest thousand dollars) for each of the seven cars of the same model.

Age (x)                                                                                  Price (y)
(years)                                                                           (thousand dollars)
3...........................................................................................28.4
7........................................................................................... 17.2
5........................................................................................... 21.6
9........................................................................................... 13.9
12........................................................................................... 6.3
8........................................................................................... 16.8
10........................................................................................... 9.4

Let age be denoted by x and price be denoted by y. Calculate

a. Σx 

b. Σy 

c. Σx² 

d. Σxy 

e. Σx²y 

f. (Σy)²