B1. During his vacation, Jan did holiday work. His earnings are shown in the table.

| Days | Earnings in EUR |
| :---: | :---: |
| Monday | 12 |
| Tuesday |  |
| Wednesday | 20 |
| Thursday |  |

A. How much did he earn on Tuesday if his average earnings for the first three days were 14 EUR per day?

B. How much did he earn on Thursday if he earned a total of 50 EUR from Monday to Thursday?

C. Given the complexity of the work he did, he had a different hourly rate each day. What was his hourly rate on Monday if he worked 1 hour and 15 minutes?

D. On Wednesday, his hourly rate was 4 EUR, and on Thursday, it was only one-fifth of Wednesday's rate. How many hours did he work on Thursday?
B1. From the equation $\frac{12+x+20}{3}=14$ we calculate the Thursday's earnings $x=10$ euros. From Monday to Wednesday, the earnings amounted to $12+10+20=42$ euros. Since the total earnings for the first four days were 50 euros, the Thursday's earnings amounted to $50-42=8$ euros.

$\mathrm{For} 1 \mathrm{~h}$ and $15 \mathrm{~min}=1.25 \mathrm{~h}$ of work on Monday, he received 12 euros. His hourly rate that day was $\frac{12 \mathrm{EUR}}{1.25 \mathrm{~h}}=9.6 \frac{\mathrm{EUR}}{\mathrm{h}}$. The hourly rate on Thursday is $\frac{1}{5}$ of $4 \frac{\mathrm{EUR}}{\mathrm{h}}=0.8 \frac{\mathrm{EUR}}{\mathrm{h}}$. For 8 euros of earnings, Jan worked 10 hours on Thursday.

A. Calculation of Thursday's earnings 10 euros. $2 \mathrm{t}$

B. Calculation of Thursday's earnings 8 euros. ... $1 \mathrm{t}$

C. Calculation of the hourly rate for Monday: $9.6 \frac{\mathrm{EUR}}{\mathrm{h}}$ $2 \mathrm{t}$

D. Calculation of the number of hours worked on Thursday: 10