Let P be the amount of invested money. Then,
.08P = 336
P = 336/.08 = 4,200
249.88 dollars
$2,500 is your answer
4000
$2400
Interest = Principal*Time*Rate = 950*4*3% = 950*4*3/100 = 114
2,400
249.88 dollars
775
1282.5
$2,500 is your answer
$810
215
$775
$43.20 more
$4,500
4000
$2400