At first, pg means picogram
[tex]1pg=10^{-12}g[/tex]A microgram is a unit to measure the mass
[tex]1\mu g=10^{-6}g[/tex]Then from both relation
[tex]1pg=10^{-6}\mu g[/tex]Now we can solve the question
Since the average mass per cell is 67.55 pg
Since the number of cells is 10^5
To find the total mass multiply them
[tex]\begin{gathered} T\mathrm{}m=67.55\times10^5 \\ T\mathrm{}m=6755000pg \end{gathered}[/tex]We need to change it to microgram, then multiply it by 10^-6
[tex]T\mathrm{}m=6755000\times10^{-6}[/tex]Put a decimal point at the end of the number and move it 6 places to the left to get the answer
[tex]T\mathrm{}m=6.755\mu g[/tex]