The Marginal Tax Rate is computed by:
  
 Change in total tax paid
 Divided by
 Change in income
  
 So in the problem:
 21000 – 18400
 Divided by
 90000 – 80000
  
 = 2600 / 10000
 = 0.26, multiply this by 100% to get the percentage
 = 26%
  
 Average Tax Rate:
 Total tax paid
 Divided by
 Income
  
 = 21000 / 90000
 = 0.2333333, multiply this by 100% to get the percentage
 = 23.3%
  
 Therefore, the answer is 26; 23.3.