Answer and Explanation:
The computation is shown below;
a. The amount of the total dollar sales is 
Pretax income = Sales value - Variable cost - Fixed cost 
where, 
Sales value - variable cost = Contribution margin 
 $365,100 = Contribution margin - $251,000 
So, 
 Contribution margin = $616,100 
Now 
Contribution margin = Sales value × Contribution margin ratio 
$616,100 = Sales value × 61% 
 So, 
Sales value = $1,010,000
b. The total variable cost is 
= Sales - fixed cost - pre tax income 
= $1,010,000 - $251,000 - $365,100
= $393,900