Answer: 2.28%
Explanation:
When they mature they will pay her $20,000 yet she bought them for $19,775.
The rate of return is a simple interest rate;
A = P * ( 1 + rt)
t = 26/52weeks = 0.5
20,000 = 19,775 ( 1 + 0.5r)
1 + 0.5r = 20,000/19,775
0.5r = 1.011378 - 1
r = 0.011378/0.5
r = 0.022756
= 2.28%