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

$\backslash$table$[[,$Total Costs,Units Produced$],[$January$,$$$1,890,000,22,500$ units$],[$February$,2,800,000,35,000],[$March$,4,230,000,55,000]]$

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