Janelle S. answered 05/21/20
Penn State Grad for ME, Math & Test Prep Tutoring (10+ yrs experience)
Not exactly sure how you got 3,125.21, but make sure you convert r into a decimal and convert t into time in years.
P = $2400
r = 9.2% = .092
t = 3 months = 3/12 years = .25 years
A = P(1 + rt) = $2400 (1 + .092*.25) = $2400 (1.023) = $2455.20