Hello, I can't figure out how to solve this question:

Consider these summary statistics for a random sample:

Mean of x=20 Mean of y=10 Sx(variance)=3 Sy=7

Sxy= -18

For which of the following straight lines would the SSE (sum of the squared errors) be SMALLEST?

a) y= 4 -6x
b) y= 8-6x
c) y= 50 -2x

The right answer is C, but i don't understand what is the calculation behind it.

Please help!