The answer is that the time period of the loan is 351 days.
Shamari takes out a loan = $10,500,
at 8.5% exact interest
If the amount of interest is = $858.03,
858.03 = 10,500 x .085 x x/365
858.03 = 892.50 x x/365
858.03/892.50 = x/365
0.961378 = x/365
x = 0.961378 x 365
x = 350.9,
rounded is 351