E$4-31.$ Multiproduct Green Rider makes three types of electric scooters. The company's total fixed cost is $\backslash (\backslash$$ $1,080,000,000\backslash ).$ Selling prices, variable cost, and sales percentages for each type of scooter follow: a$.$ What is Green Rider's break$-$even point in units and sales dollars? b$.$ If the company has an after$-$tax income goal of $\backslash (\backslash$$ $1\backslash )$ billion and the tax rate is $50$ percent, how many units of each type of scooter must be sold for the goal to be reached at the current sales mix? c$.$ Assume the sales mix shifts to $50$ percent Mod, $40$ percent Rad, and $10$ percent X$-$treme. How does this change affect your answer to $($a$)?$ d$.$ If Green Rider sold more X$-$treme scooters and fewer Mod scooters, how would your answers to $($a$)$ and $($b$)$ change? No calculations are needed.