Someone puts 5000 francs into a savings account, how much money will they have at the beginning of the 20th year, if starting from the third year, they add 350 francs at the beginning of every second year? $p=4$.
Let the capital paid at the beginning of the first year be $t$, each installment $r$, the number of years $2 n$, and the interest factor $e$.

The value of the amounts paid at the beginning of the 1st, 3rd, 5th, ..., $(2 n-3)$th, $(2 n-1)$th years at the beginning of the $2 n$th year: $t e^{2 n-1}, r e^{2 n-3}, r e^{2 n-5}, \ldots r e^{3}, r e$. Therefore, the value of the capital at the beginning of the $2 n$th year is:

$$
T=t e^{2 n-1}+r e \frac{e^{2 n-2}-1}{e^{2}-1}
$$

Substituting the given numbers:

$$
T=5000 \times 1.04^{19}+350 \times 1.04 \times 100 \frac{1.04^{18}-1}{4 \times 2.04}
$$

Performing the calculations, we get:

$$
T=15107 \text { Ft }
$$

The problem was solved by:

Friedmann Bernát, Grünhut Béla, Hofbauer Ervin, Kántor Nándor, Szabó István.