The number of a company's Model CT curved screen ultra high definition televisions (Q) that will be sold in the next year depends on the number of dollars spent on production, x, and the number of dollars spent on advertising, y, according to the function Q = 0.72 x^0.5y^0.75+ 6400 What is the rate of change of sales with respect to advertising expenditure if x =472783, y=65531 ? Give your result rounded to the nearest integer.