Starting money = $350. Interest rate = 2.5%
Time - 3 years.
How much interest?
a) $7.50
b) $26.25

Step-by-step explanation:

I=Prt

I=350(0.025)3

I=$26.25

Sample size, n = 75
Point estimate, p = 52/75 = 0.693
Z at 99.7% confidence interval ≈ 2.96

Population mean interval = p+/- Z*Sqrt [p(1-p)/n]

Substituting;
Population mean interval = 0.693 +/- 2.96*Sqrt [0.693(1-0.693)/75] = 0.693+/-0.158 = (0.535,0.851) or (53.5%,85.1%)