Hess's law can be used to evaluate complex chemical reactions' enthalpy. Consider the following set of chemical reactions and answer the follow up questions.

$2C{O}_2(g)+H_{2}O(g)C_2{H}_2(g)+\frac{5}{2}{O}_2(g),H=???$

$C_2{H}_2(g)+2H_2(g)C_2{H}_6(g),H=-94\mathrm{.}5kJ$

$H_{2}O(g)H_2(g)+\frac{1}{2}{O}_2(g),H=-71\mathrm{.}2kJ$

$C_2{H}_6(g)+\frac{7}{2}{O}_2(g)2C{O}_2(g)+3H_{2}O(g),H=-283kJ$

a$.(7\%)$ What is the change in enthalpy of the synthesis of ethyne?

b$.(4\%)$ Can you estimate the time it would take to produce $10$ moles of ethyne at $50C?($you can assume mixing of different chemicals occurs instantly$)$