6. Joker and Harley Quinn plan to earn money by mining cryptocurrencies. For mining, they chose Ethereum (Ethereum) as one of the most stable and promising currencies. For this, they bought a system unit for 9499 rubles and two video cards for 20990 rubles each. The power consumption of the system unit is 120 W, and each video card consumes 185 W. The mining speed on one video card is 23 million hashes per second, allowing them to earn 0.00630 Ethereum per day on one video card. 1 Ethereum equals 27790.37 rubles. How many days will it take for the heroes' investments to pay off, considering the cost of electricity at 5.38 rubles per 1 kWh? (20 points)

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# Answer:

With two video cards, you can earn $2 \times 0.00630 \times 27790.37 = 350.16$ rubles per day. The power consumption of one system unit and two video cards is $120 + 185 \times 2 = 490$ watts per hour, or 11.76 kWh per day, which amounts to 63.27 rubles spent on electricity per day. Capital expenses amount to 51479 rubles, and the income for 1 day is $350.16 - 63.27 = 286.89$ rubles. Thus, the system will start generating profit after 179.44 days, assuming the mining difficulty remains unchanged.

## Grading Criteria:

20 points - for correctly conducted calculations (a difference of no more than 1 day from the reference solution due to rounding errors is allowed);

15 points - for correct logical reasoning, but with arithmetic errors;

10 points for correctly calculated electricity costs / correctly calculated mining income;

5 points - for providing the correct calculation of electricity consumption or income[^0]


[^0]:    Maximum score for the task is 100 points.