Each of Exercises 61 through 68 involves either the chain rule for partial derivatives or the incremental approximation formula for functions of two variables.

At a certain factory, when the capital expenditure is K thousand dollars and L worker-hours of labor are employed, the daily output will be Q = 120K^1/2L^1/3 units. Currently capital expenditure is $400,000 (K = 400) and is increasing at the rate of $9,000 per day, while 1,000 worker-hours are being employed and labor is being decreased at the rate of 4 worker hours per day. At what rate is production currently changing? Is it increasing or decreasing?