Explanation:
income is based on a formula (rt)
r is a % of p (% being Annual Interest)
t is time (number of years)
p is principal.
17. 9,600$ in interest (lost or gained, gained is added from p, lost is subtracted from p)
18. is 1,750$
I am not entirely sure what interest periods are but I assume you can use this formula to find it. good luck man.