Respuesta :

[tex]\bf 4\frac{2}{10}~ug\implies 4\frac{1}{5}~ug\implies \cfrac{4\cdot 5+1}{5}\implies \cfrac{21}{5}~ug[/tex]

as far as I can tell, "u" being the prefix for "micro", or just use the longhand "micrograms".
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