i cant understand this question :|

#1
Hi everyone , i had small problem with this question i don't know what Sxx Syy Sxy and C.I mean?
i wanna find the roles to follow but i couldn't

A new-car dealer is interested in the relationship between the number of sales-people working on a weekend and the number cars sold .Data were gathered for six conservative Friday
______________________________________
no of sales people(x)| 5 |7 | 4 | 2 | 4 | 8 |
no of cars sold(y) | 22 | 20 | 15| 9 | 17| 25|

Given that Sxx=24 ,Syy=160 ,Sxy=56 and SSE=29.333
a. Determine the estimated regression line.
b.How much of the variation in the number of automobiles sold is explained by the number of salespeople?
c. Estimate the mean of squares of errors .
e. Test the null hypothesis that the number of sales does not depend on the number of salespeople working?
f.Find the 95% C.I for the aveage number of cars sold when the number of salespeople working is 10

if anyone can help me to get god understanding in Linear regression send me Privet Message and i'll contact him\her
:D