with detailed solution typewritten ill rate later reference on comment section

4. (Ipts.) Given the total-cost +12Q+75, write out a variable-cost (VC) function. Find the derivative of the VC function and interpret the economic meaning of that derivative. 5. (Ipts.) Given 3x2y3 +x:2y2 + y3zr4 + y2: O , use the implicit function rule to find and . 6. (Ipts.) Find the rate of change of output with respect to time, ifthe production function is Q = , where A(t) is an increasing function oft , and K = Ko + at , and L=L0+bt.