$287.64
Calculate the interest for each year, then add it to the principal for the next year.
Year 1: 250 * .06 = 15
New balance 250+15 = 265
Year 2: 265 * .07 = 18.55
New Balance 265+ 18.55 = 283.55
Year 3: 283.55 * .08 = 22.68
New Balance 265+ 22.68 =287.64