Hello Georgette,
The formula for simple interest is I = Prt. P is the principal (amount invested or deposited), r is the interest rate; t is the duration of investment or deposit.
To answer your question, let's find and compare Paul and Monica's interest after 1 year:
Interest for Monica = 200*0.033*1 = $6.60
Interest for Paul = 300*0.031*1 = $9.30
Paul will get more interest after 1 year, so Monica was not correct.
Cheers.