Task 3. A master and an apprentice need to make a concrete slab with dimensions $4 m, 3 m$ and $20 \mathrm{~cm}$, as well as 4 fence posts with dimensions $20 \mathrm{~cm}, 3 \mathrm{~m}$ and $25 \mathrm{~cm}$. The master told the apprentice to calculate and order the exact amount of concrete needed. The apprentice calculated that they need to order $30 m^{3}$ of concrete. Did the apprentice make a mistake in the calculation?