Abudget constraint model differs from a ppf model in that it is a line and represents units of measurement.

Straight line and vague units of measurements. These are the differences between a budgetary restriction model and an of the model. This is because the first model represents a strategy of restricting budgets and expenses and the second one works with vague and random units that are selected at the convenience of what is going to be required.

I'm not 100% sure but i think it is service producing industries 

Answer(a) stop payment on the first check; then write a second one;