Which if the following statement does is true about variable expenses

Variable expenses are typically one time expense. Due to them varying, it's not always going to happen again, if they know the expenses will happen again, they are known as fixed expenses and can budget for them. Recurring expenses that happen at different times for different amounts are also variable expenses. Though it's hard to budget exactly for what the variable expenses will be, it's best to have a variable expenses budget to make sure the spending it kept under control. 

Answer consumption and investment; net exports       (or)                           real interest rate ; ; ; ///   exchange rate;