Effective Rate of Interest

[lance7tour]

The treasury department actioned $21 billion in 3-month bills in denominations of 10000 dollars at a discount rate of 4.965%. what would be the effective rate of interest? round answer to the nearest hundredth percent

How would I start this problem.

thanks

 

[lance7tour]

(1-.04965) * 10000 = 9503.50

9503.50 x .04965 x 90/360 = 117.96

117.96 ___________
(9503.50 x 90/360)
= 117.96 / 2375.875
= .04965 or 4.97%

is this right?