In a Multiple Regression Model $y ^ { \prime } = - 9 + 3 x _ { 1 } + 21 x _ { 2 } + 13 x _ { 3 } + 4 x _ { 4 }$

Multiple Choice

In a multiple regression model $y ^ { \prime } = - 9 + 3 x _ { 1 } + 21 x _ { 2 } + 13 x _ { 3 } + 4 x _ { 4 }$ , if the $x _ { 1 }$ value changes by 2 , then the predicted value for $y$ will change by

A) 32
B) 6
C) -3
D) 42