$5.$ Cena Inc. has decided to use the high$-$low method to estimate the total cost and the fixed and variable cost components of the total cost. The data for various levels of production are as follows:

Month Units Produced Total Costs

April $80,000$ $$25,289,000$

May $99,00027,785,600$

June $125,00031,202,000$

July $81,00025,420,400$

a$.$ Determine the variable cost per unit and the total fixed cost.

b$.$ Based on part $($a$),$ estimate the total cost for $115,000$ units of production.