With reference to calculation of trend values if $n =7, ∑y= 630, ∑xy = 56 $ and $∑x^2 = 28,$ select the correct statements ?

(A) The value of 'a' of straight line trend is 2.

(B) The value of 'b' of a straight line trend is 2.

(C) Straight line trend equation is represented by $y = a- bx.$

(D) The algebraic sum of deviation of the actual values from trend values is -1.

(E) In a free hand curve method the area above the trend line should be almost equal to the area below it.

(B) and (E) only