The manufacturing costs of Schroeder Industries for the first three months of the year follow:

$\backslash$table$[[,$Total Costs,Units Produced$],[$January$,$$$3,750,000,40,000$ units$],[$February$,3,875,000,45,000],[$March$,4,250,000,60,000]]$

Using the high$-$low method, determine $($a$)$ the variable cost per unit and $($b$)$ the total fixed cost.

a$.$ Variable cost per unit $

b$.$ Total fixed cost :