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 interest (I) of the current investment (P) according to simple interest (i) is, 
                                        F = Pin
where n is the number of interest period.
For Sam's investment,
                              F = ($9400)(0.052)(7) = $3421.6
For Pat's investment,
                              F = ($9400)(0.06)(7) = $3948

Thus, the difference between their interests is $526.4. Thus, the answer is letter D.