請教一下
Mary invested $8400 for 6 months in a certificate of deposit paying 9 1/4 percent simple annual interset. How much more interest would Mary have received if the interest rate on this certificate had been 9 3/4 percent simple annual interesst?
A $2.10
B $21.00
C $42.00
D $210.00
E $420.00
謝謝唷!!