The prices of inputs (x1, x2, x3, x4) are (4, 1, 3, 2).
(a) If the production function is given by f(x1, x2) = min{x1, x2}, what is the minimum cost of producing one unit of output?
(b) If the production function is given by f(x3, x4) = x3 + x4, what is the minimum cost of producing one unit of output?
(c) If the production function is given by f(x1, x2, x3, x4) = min{x1 + x2, x3 + x4}, what is the minimum cost of producing one unit of output?
(d) If the production function is given by f(x1, x2) = min{x1, x2} + min{x3, x4}, what is the minimum cost of producing one unit of output?