The graphs of functions f(x) and g(x) = f(x) + k are shown:

graph of line f of x going through ordered pairs 0, negative 2 and 2, 2. graph of line g of x going through ordered pairs 0, 2 and 1, 4.

what is the value of k?

k = −2
k = 2
k = −4
k = 4