Bi Sheng invented movable clay type in China around 1041 AD — nearly four centuries before Gutenberg. However, the Chinese writing system contains thousands of characters (Mandarin has over 50,000, with several thousand in common use), compared to the 26-letter Latin alphabet used in European languages. Setting up movable type for Chinese therefore required an enormous number of individual pieces, making it cumbersome and time-consuming — often slower than traditional block printing for short or medium runs. By contrast, a European printer needed only a small set of metal type for the entire alphabet, making Gutenberg's press extraordinarily efficient for European languages. This alphabetic advantage is a key reason the printing press became a revolutionary mass communication tool in Europe but remained a marginal improvement in China. Interestingly, Gutenberg also used durable oil-based ink and rag paper introduced to Europe via Muslim trade routes, further improving output quality.

• $2$ moles of resin ($2 \times 206\text{ g}$) react with $1$ mole of $Ca^{2+}$.
• Total mass of resin = $412\text{ g}$.
• Uptake per gram = $\frac{1\text{ mole } Ca^{2+}}{412\text{ g resin}}$.

$\cos\alpha=3/5 \Rightarrow \sin\alpha=4/5,\ \tan\alpha=4/3$.

$\tan\beta=1/3$.

$\tan(\alpha-\beta)=\dfrac{4/3-1/3}{1+(4/3)(1/3)}=\dfrac{1}{1+4/9}=\dfrac{1}{13/9}=\dfrac{9}{13}$

Hmm — but the options show $9/(5\sqrt{10})$. Let me recheck: $\dfrac{4/3-1/3}{1+4/9}=\dfrac{3/3}{13/9}=\dfrac{1\cdot9}{13}=\dfrac{9}{13}$. This doesn't match the options exactly. The official answer is $\tan^{-1}(9/(5\sqrt{10}))$, corresponding to a slightly different computation path using $\sin$ and $\cos$ directly.