For what values of b, the system has infinitely many solutions?
x₁ + 2x₂ - 3x₃ = 4
4x₁ + x₂ + 2x₃ = b + 2
3x₁ - x₂ + 5x₃ = 5

a. 7
b. 4
c. 2
d.-2
e. 0