Ernie deposited $4000 between two savings accounts. one account paid 4% simple interest and the other paid 2%. at the end of one year, ernie had earned $140 in interest for both accounts. how much money did ernie deposit in the account that paid 4% interest?
a)$2000
b)$2500
c)$2800
d)$3000

Ernie deposited D.) 3000 to the account that paid 4% interest

Simple interest is computed by multiplying the principal to its rate and term.

SI = P * r * t

Since there are two accounts and two interest rates, I did a trial and error computation. It may be tedious but it gives the correct answer.
Account 1     Interest 4%     Account 2    Interest 2%    Total Interest    
4,000.00            160.00                 -                 -                     160.00   
3,000.00           120.00         1,000.00         20.00                   140.00   
2,000.00             80.00         2,000.00         40.00                   120.00   
1,000.00            40.00          3,000.00         60.00                   100.00           
    0                     0                4,000.00         80.00                     80.00
  

Then just do it (lol)