Given several values of x, y and z in the relation z=ax+by+c, determine a, b and c

Question

I have inherited a cloud pricing mechanism that essentially uses two variables to derive prices. No-one in the organisation knows the original derivation, but I have about 16 sets of datapoints from which I am hoping to reverse-engineer the mechanism. That should help derive new or future pricing - or trigger a change of policy! Hence, given some known values of x, y and z in the relation z=ax+by+c, how might I determine a, b and c? Many thanks in advance.