Hello,
a) You have to know : Amount = Principal + interest
Therefore :
Amount : [tex]4000 + 960 = 4960[/tex]
b) You have to learn this by heart too , the formula for rate
R = [tex] \frac{100*I}{PT} [/tex]
Therefore :
[tex]R= \frac{100*960}{4000*3} [/tex]
[tex]R = 8[/tex]
The answer would be 8% per annum.
c) If the rate was 1% more, it would give R = 8 + 1 = 9% per annum.
Afterwards, the formula for Interest is : [tex]I = \frac{PRT}{100} [/tex]
Therefore :
[tex]Interest = \frac{4000*9*3}{100} = 1080 [/tex] $
So in her account, if the interest was 1% greater, the amount in her account would have been :
$4000 + $1080 = $5080.
That gives $5080 - $4960 = $120 more dollars in her account if the interest rate were 1% greater.
You won't need help in this exercice anymore ! :D
Hope this helps !
Photon