Sam invests $9,400 in a fund yielding 5.2% simple interest annually. at the same time, pat shops around for a better interest rate and invests $9,400 in a fund yielding 6.0% simple interest annually. after seven years, how much more interest has pat’s fund earned than sam’s fund?
a.
$817.80
b.
$3,948.00
c.
$652.40
d.
$526.40

The accumulated interest of money with simple interest rate for n years may be calculated by: 
 
                                                I = Pin

where P is the principal and i is the interest rate. 

For Sam's case the interest is,
 
                                  I = ($9,400) x 0.052 x 7 = $3,421.6

For Pat's, 
 
                                  I = ($9,400) x 0.06 x 7 = $3,948

The difference between their interests (D),
 
                                   D = $3,948 - $3,421.6 = $526.4

Thus, the answer is letter D. $526.4

Definitely