Answer:
At the beginning of 6th month , Jeff will have in his account $ 520 .
Explanation:
At the beginning of 6th month , Jeff will have in his account,
$
![( 100 * (1 + 0.02* 4) + 100 * (1 + 0.02 * 3) + 100 * (1 + 0.02 * 2) + 100 * (1 + 0.02) + 100)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/bdi9joyhd3hkfoaak8p5wmgjjanfi97jb6.png)
= $
![(100 * (5 + 0.02 * (4 + 3 + 2 + 1)))](https://img.qammunity.org/2020/formulas/mathematics/middle-school/kw1j58c8m44qan5rkehc8ojdefdcwhcbsv.png)
= $
![(100 * (5 + 0.02 * 10))](https://img.qammunity.org/2020/formulas/mathematics/middle-school/vgx453exhanf0sqcuu6so5a2us5yapx60z.png)
= $
![(100 * 5.2)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/6xh2ns8zl167mbjp9tqrl3yyse1tjyt0dd.png)
= $ 520
since, the $ 100 deposited at the end of 1st month earns interest for 4 months till the end of the 5th month, the $ 100 deposited at the end of the 2nd month earns interest for 3 months and so on till the last $100 deposited earns interest for '0' month.