b 650000+320000 * 3.87 = 1888400

C because:10 * 320000-1888400 =1311600 > 0 so yes

D suppose the selling amount is x: 650000+190000+x * 3.87 <; 10 * X X & gt； 137030.995

Xmin= 13703 1

2. operating leverage, also known as operating leverage or operating leverage, refers to the law that the change rate of profit is greater than the change rate of production and sales due to the existence of fixed costs in the production and operation of enterprises.

Operating leverage coefficient = change rate of earnings before interest and tax/change rate of production and sales volume = marginal contribution/(marginal contribution-fixed cost) Failure to dismiss means increasing fixed cost in disguise, so it can be seen that the operating leverage coefficient becomes larger by substituting into the formula; Because the greater the operating leverage coefficient, the greater the role and operational risk of operating leverage, so the greater the operational risk of enterprises.