Answer:
a. $36
b. $336
Explanation:
The simple interest on a amount is:
A=P(1+rt)
A is the amount after interest, P is the amount before interest, r is the rate of interest and t is the time in years.
a.
We can use the formula:

The interest earned is the amount after interest minus the original amount before interest:

$36 of interest was earned
b.
The balance of the account is $336 worked out in a