For the system of equations 3x + y = K + 1, x + 3Y = 3 and X + y is nonnegative, then the range of K is?

For the system of equations 3x + y = K + 1, x + 3Y = 3 and X + y is nonnegative, then the range of K is?


By deforming ① and ② respectively, x = 3K / 8 and y = 1-k / 8 are obtained
Then x + y = K / 4 + 1
X + y is greater than or equal to 0
Then K is greater than or equal to - 4