If the function \(\rm {f}(\mathbf{x})=\left\{\begin{array}{cc} 1, & x \leq 2 \\ a x+b, & 2 is continuous at x = 2 and 4, then the values of a and b are.
1
a = 3, b = −5
2
a = −5, b = 3
3
a = −3, b = 5
4
a = 5, b = −3