Your weekly cost (in dollars) to manufacture x bicycles and y tricycles is C(x, y) = 36,000 + 90x + 40y. Calculate and interpret ∂C/∂x and ∂C/∂y.
The marginal cost to manufacture bicycles is the partial derivative of C with respect to x, which is dollars per bicycle.
The marginal cost to manufacture tricycles is the partial derivative of C with respect to y, which is dollars per tricycle.
The marginal costs do not depend on the production level, since the cost function is linear.